“The way faith has panned out today in America would have Jesus running for the hills”

Third person pronouns are normal, one of the endearing Amos tics. Her husband, the English sound-engineer Mark Hawley, is called Husband; their daughter, Natashya, is referred to as Child. And Tori, born Myra Ellen Amos in North Carolina 43 years ago, is Tori, and occasionally Mum. The shards multiply further in American Doll Posse, her ninth studio album, which features personas based on the women of the Greek pantheon. Hence Isabel (Artemis), Clyde (Persephone), Pip (Athena), Santa (Aphrodite) and Tori (Demeter and Dionysus) all make sporadic appearances. It's a trick she has flirted with before on Strange Little Girls (2001), where she interpreted male artists' songs from a female perspective, and Scarlet's Walk (2002), where Scarlet was the singer's wandering alter ego. The new album surpasses both of these in its reach and political scope.

"There were extreme musical styles happening from the beginning and the producer side of my brain had to start making assessments," she says. "I had to decide what Tori's role was. We had to have a chat with the artist and she agreed that this was not a typical singer-songwriter record. I think she was ready for a change so then I could push the go button."

Prime targets on the album are America, its god and its women. Bush gets a kicking in the track Yo George, an echo of his infamous "Yo Blair" at last year's G8 summit in Russia. He has the country where he wants it, she sings, "on all fours." Bush's triumph in the 2005 US election was a victory for the Christian right, she says, but not for women.

Hillary Clinton - the possible Democrat contender for the presidency next year - has the kudos to mount a strong female challenge, if not the trust of the female voters ("she's qualified - that's not the issue"). With songs such as Fat Slut and Girl Disappearing, Amos talks of weaving a tale, a kickback to her Scottish weaving ancestors, of dodging the stereotypes carved out by "Christian America" and creating new paintings for women to step into. It could be distancing, but the result is relentlessly intimate.

"I think the women and their stories are very tangible," she says. "There's a lot exposed there and smart people know that secrets are usually hidden right in front of them by the good creators. You have to remember that for me to go after something destructive, my answer is always to do something creative. And sometimes you have to really, really create to even match the ferocity of the destruction."

Raised in Maryland but a resident of Cornwall for the last 10 years, Amos spent time observing women, of the American variety, for the new album, taking in reactions to Janet Jackson's breast flop at the Super Bowl in 2004, scanning the no-knickers society girls of the Paris Hilton mould.

"You just think, this is like a little girl trying to get back at daddy," she says, "and yet where is the real love for what your sexuality can do?" Like a feminist Christmas, the album unpacks the boxes that women are put into by men, by society, by themselves. She hasn't given up on her fellow sisters, but says "it's sometimes the women that can be most vicious to each other."

Her talk veers from writers like Gloria Steinem to the "hairy bikers" - with whom she appeared recently on Loose Women - from Radio 1 DJ Chris Moyles to the scribes of the Gnostic gospels. It's as if they form part of the same canon. All are called upon to illustrate her arguments, like reference points on an internal map. She wants to unpick the stitching of the Virgin Mary, "who has no sexuality", and Mary Magdalene, "who has her sexuality but no respect or sacredness", reworking both into a pliable and acceptable form. The way the faith has panned out, and particularly in present-day America, she says, would have Jesus "running for the hills." Over the years, the topic has been a flashpoint with her father - a Methodist minister - and her mother, a part Cherokee Christian.

"They believed anything that wasn't approved of by the church fathers shouldn't even be considered," she says. "I keep saying that the church fathers were just these guys, no different from George Bush or Tony Blair. I mean, could you imagine if George Bush decided which music you could listen to? It probably wouldn't be John Lennon."

For all her complaints against organised religion, it is patently still important, if only as something to kick against. Publicity shots for the new album show Amos with the Bible in one hand, the word "shame" written on the other, and blood trickling down the inside of her legs. It's a startling image, and one the Mexican artist Frida Kahlo would have been proud of.

"The blood of a woman is something so intimate and private," she says. "It's the blood that doesn't come from violence, and yet we've been violently incriminated because of it, as something to be judged and controlled by the Christian authority. But it has nothing to do with them, it's ours, we need to claim it."

The battle cry extends to her daughter Natashya, who Amos does the odd impression of. With hands wriggling above her head, followed by a child's voice and facial expressions, it's really quite convincing. The six-year-old is now at an age where her mother's many faces have to be unpeeled and kept in different jars. For Amos, it's about explaining the difference between the banshee and the babysitter.

"If she's not feeling right with the songs she doesn't have to listen," she says. "It could be scary for her to see the woman confronting the energy force because it's not warm and fuzzy mum. Once she understood the difference I began to pick up the ever-present tomahawk that I quietly lay down, especially when I pick up the little girl. I put it right on my hip to take a look at what was going on."

She remembers the precise dates of her three miscarriages - in 1996, 1997 and 1999 - like birthdays of a sort. Twice they occurred more than three months into the pregnancy, and once a little earlier. The good news, and the bad, was that the hospital could find nothing wrong, and thus nothing to change, leaving Amos with the impression that she could "carry all these song children, hundreds of them, but not a human life."

The doctors advised getting back to basics with her husband Mark Hawley, taking a break and being a regular couple, which is exactly what they did. The pair spent time on the water, cooked meals and took it easy. Still grieving their loss, they discovered in 2000 that Amos's stomach flu wasn't really flu after all. She was pregnant.

"I wouldn't wish the miscarriages on an enemy, much less myself," she says, "but I didn't have my priorities right. I'm still a road dog, but now we cater to Child. It wasn't a case of she's got to fit in with us', which is how it would have been before. We work together. The guys coming out on the road want to be on Tash's bus now because she's fun. It's done everybody a lot of good to have her around."

It was eight months into her pregnancy with Natashya that Tori - or yet another version of her - was born. Abnormally big due to a protein deficiency, and taking shots of heparin twice a day in her leg to prevent blood clots, she says she was fast becoming a "beached whale" - poked and prodded, but in her prime. "Miraculously I really felt sexy and pure for the first time" she says. "I thought about it later when Tash was a baby, when I would play the piano for hours while she sat beside me. The idea came to me that this willing invasion of a child that I agreed to have had somehow kicked out the other opinions I had taken on and didn't know how to get rid of."

She describes herself as a recluse but acknowledges the paradox given her international status. In many ways, personal trauma has been a mainstay of her recording career. Her brother Michael, who died in a car accident in 2004, is remembered on The Beekeeper album (2005); the break-up of her seven-year relationship with producer Eric Rosse was covered in Boys For Pele (1995); her rape by an obsessed fan at gunpoint was revisited on her breakthough album, Little Earthquakes (1992). The attack led her to co-found the Rape Abuse And Incest National Network (Rainn) in 1994, a US helpline to connect rape victims with local crisis centres. Even now, she has recurring nightmares where there is "always an intruder, and always right there."

"One time I gave Husband a black eye," she says. "I didn't mean to, but I really believed somebody was there. I think some of it is just the past. When you do something on that level, when you really abuse somebody else's right and invade them, the ramifications are very hard to track. This stalker who has no body and no face is something I've been contending with for a long time."

As a consequence, she prefers cat naps to sleeping, natural sedatives to the synthetic, more powerful, kind. "The idea of a sleeping pill is just the scariest thing in the world to me. As a lioness, the idea of being knocked out so I can't fight is really not acceptable."

On advice from Peter Gabriel in 1995, the lioness gradually took more control of her music, shifting 15 million records and becoming one of only a handful of women to secure five or more US Top 10 albums in the process. The fighting spirit saw her enroll as the youngest ever music scholar at Baltimore's prestigious Peabody Conservatory, aged five, before being asked to leave at 11 for her wayward approach to sheet music.

She has owned Martian Studios in Cornwall with Hawley since 1997, where she hires the engineers, owns the master tapes and protects her integrity fiercely. It's an achievement she clearly appreciates. Little Earthquakes was the result of a four-year battle with record label Atlantic, who wanted to promote her as as a rock chic and replace her trademark Bösendorfer piano with heavy guitars. Her contract with the label ended with the delivery of her remastered hits package, Tales Of A Librarian, in 2003. "Peter Gabriel didn't say this, but checkmate motherf*cker," she says now. In her struggle, she acknowledges something of the Calvinist. "People don't ask me what I got from the Scottish side and, you know, with all my mother's mysticism, there's a tenacity that my father gave me, a discipline. I got the fire and the tomahawk to stand up to the corporate music business from my mother, but it was also about having the ability and the patience to wage the war."

Her good dreams come complete with a company of players, which she describes as her musical fantasy, the songs presenting themselves subconsciously as as "a gift" she can later work with. Such was the case during last year's summer solstice, when she woke at four in the morning and began scribbling frantically on the backs of books. She ran over to the studio to begin recording and, by the time the house awoke, she had finished. The track - Big Wheel - is the first single to be taken from the new album. Its refrain - the acronym Milf (which doesn't mean "mother I'd like to fondle" but comes close) - was the only part taken from her waking life, not dreams. "Yeah, that was my contribution," she says "I love that word." It's another reflection, another shard.

"If you asked me where I could stop time it would be now, at 43," she says. "To wake up feeling sensual and wanting to be in my body - I don't want to be who I was at 30. I know I've aged, that there are things I don't possess any more, but it's how I feel inside. I'm willing to accept the lines and everything that comes with them because the feeling of being a woman, right now, is something I really treasure. That and being a mother and being in a relationship with a man I really adore."

She is no longer the ingénue, nor the oldest in her family, but somewhere in-between. Her mother - a 78-year-old heart attack survivor who "used to take 11 medications just to stay alive" - takes her to stand in front of the mirror at home in America, where she offers simple but effective advice.

"She wants me to really appreciate where I am," says Amos, "and says that all too soon I will be a grandmother. She says, When I look in the mirror, I wonder who that woman is. I'm running in a field, I'm dancing with your father in high heels. I'm not this old woman, this is not who I am.' When it comes from that place, you think, can I take this great wisdom? And so, yes, I'm trying."

Finding peace with her late paternal grandmother ("I always said she would be one of the ones burning witches") has seen Amos make several pilgrimages to Scotland. She explains the Native American belief that answers often lie with one's ancestors, though separated by place and time. "I went to Iona and seemed to find some kind of reconciliation," she says. "It wasn't as if I saw a vision - I just walked around for several days. But there seemed to be a peace made, an awareness that my grandmother did the best she knew how at the time. I was even going to name Tash Iona but didn't think it was right to subject her to that story."

That a journalist, and a Scottish one, hasn't yet been to the island comes as a surprise. "You have to go," she says. "Spend some time there, it's unbelievable. Promise you'll go and say that Tori says hi' to the ghosts of the women."

A man appears at the door, sticks his head in. Amos has her back to him but is facing a mirror. She smiles at her own reflection and his. "It's funny, I think the artist did come and talk to you today, but it doesn't always happen," she says. "You'd be surprised... at least once a day an intruder walks into the room."

American Doll Posse is released on Tuesday May 1. Tori Amos performs at T In The Park on July 8