Rightly or wrongly, the use of the word cartoon to describe the fine art of satirical caricature has become commonplace following last week's attack on the office of the French magazine Charlie Hebdo. Roy Petrie is quick to point out the difference between them. Although much of his illustrative work in newspapers - as design executive at The Herald from 1988 until 2009, and at the Daily Express and Daily Record before that - might now be recognised as cartoons, he prefers the term caricature because it has always been associated with satire. Readers of the Herald may recall his various representations of Gordon Brown, one of the artist's most difficult subjects due to the longevity of his office as a Labour MP, Chancellor, party leader and PM. "I didn't enjoy the sight of him, and was once reprimanded by the editor for showing it," he says. Margaret Thatcher sitting astride the Trident and being carried aloft by what he calls her "Cabinet toadies" made the front page of the Daily Record.

"I never wanted to be a cartoonist because it ties you to the current news agenda and means you're destined to repeat the same style over and over again," he explains. "Satirical caricaturist was a term I enjoyed because it allowed you to make a political point, either obliquely or directly, in a variety of styles using references from the person's past as well as the present. Caricature allows you to puncture the inflated sense of self which comes from power of office."

Despite its presence on and mainsteam press and across social media , the artform is a relatively recent arrival. At the Express, which he joined in 1965, Petrie asked if he could draw members of the Royal Family or the Pope and the reaction was a definite no; postwar Britain was extremely deferential to figures of authority. Eventually however he persuaded his editor to give him permission to draw the young Prince Charles, the late Pope Pius XII and Lord Mountbatten - subjects deemed too low down the pecking order to cause offence. "The caricature of Louis Mountbatten from the early 1970s changed everything, because he wrote to the paper to congratulate it on the drawing and to ask for it to add to his collection," says Petrie. "From then on, editors' attitude towards caricatures did a complete sea-change and they became acceptable in the mainstream media."

Petrie was drawing caricatures from an early age and at 17 they began to be published in the Evening Citizen. On the strength of those he got a job as Art Sub-editor on its sister title The Daily Express, starting with two small drawings a day to illustrate the television listings - only to get "dogs' abuse" from readers for distorting their favourite TV personalities. "One angry letter writer described me as a 'long-haired jumped-up degenerate'," he smiles wryly. He refused a job with the paper in London when the Glasgow office closed, deciding to start his own business, which he ran for 14 years until Arnold Kemp, the late former editor of The Herald, offered him the post of design executive.

Does he feel there's a different expectation of satire now? "It's more accepted now. In the 1960s the only place you could see extreme caricatures was in Private Eye; now you see them everywhere. Satire is more direct and in-your-face now, as it should be. Society has changed and with it the old attitude towards figures of authority, be they politicians, doctors or religious leaders. Now we question everything and that's healthy. Mockery is valid within a free society, but perhaps we're running risks in the more volatile world situation. While I think it's wonderful to see the reaction to the atrocity of Charlie Hebdo, it's a time when we should be looking to the cause of it more closely."

During his time on newspapers, Petrie continued painting privately to help support his growing family, and has had a string of successful exhibitions and commissions.

Satire was the last thing on his mind when creating the 14 pictures for Forgetfulness, an exhibition to commemorate the 70th anniversary of the liberation of Auschwitz-Birkenau by Soviety Troops on January 27 after more than one million Jews had been murdered by the Nazis in the gas chambers or through hunger, disease, torture, execution and horrendous medical experimentation.

"I'd always been interested in the Holocaust and its consequences and how we have dealt with it," he says. "I visited the Treblinka site and learned how the ashes and bones had come up through the soil decades later. Auschwitz, the largest concentration camp, is still breathtaking." Though not particularly religious himself, his reaction to the experience was irrepressible. "I felt a strong sense of injustice for the victims, and horror that such perverted people could control a nation that has given us so much culture in the past. I hope the exhibition will trigger debate and discussion on the subject. Even 70 years on, we are still discovering new information about what went on during the Holocaust. There's a sense of this being the last chance to hear first-hand from survivors. Recent history from around the world tells me we have much to learn from it. It's vital it is not forgotten."

The three paintings that make the striking triptych centrepiece, deliberately hung asymmetrically, are entitled Fire, Music, Wound, and depict Jewish history before the Nazi era. It was painted two years ago and when shown in a Glasgow synagogue recently, Petrie was approached by Moniak Garber, a Polish survivor of two concentration camps who told him that when he was a boy his father had been shot in the street by the Germans for refusing to organise the transport of Jews. He himself had been sent to Auschwitz and eventually liberated by the Russians, only to be sent to a Gulag in Siberia. He'd found his way to Glasgow and become a physicist. "He looked at my triptych and told me I needed a fourth painting and that it should be about forgetfulness," he says. "I struggled with that for a while. Should I do another painting, or alter the third? Then it came to me. I changed the title of the whole exhibition to Forgetfulness."

Ten new canvases are unframed, monochrome and abstract. Fixed crudely to the wall with parcel tape they are ripped, scorched, punctured. The sense of raw pain is palpable, and they seem to invite the viewer to touch them, to engage in a visceral connection with the past. Such immediacy is a rare achievement for any artist, and Petrie is quietly pleased.

"The Holocaust is the story of mankind, not just a Jewish or Romany story," he says pensively. "It's an episode in human history that is more obscene than genocide and yet it has still not been addressed properly. You only have to look at recent genocides in Bosnia and elsewhere and the failed attempts to bring their perpetrators to justice to realise that we have not come that far. Families are still suffering and the bodies that are being exhumed from mass graves have still not been identified.

"We have to keep the Holocaust in people's memories, because unfortunately I'm inclined to agree with Primo Levi, who believes it could happen again in our lifetime. It's almost unbelievable that people like Hitler could get away with that level of atrocity, but then you see the unrest in Europe, the destabilisation of our economies, the growing army of the dispossessed ...."

He adds that the "largely negative" reaction of some people to his new collection has been an unwelcome surprise. "It made me think they were anti-Semitic, perhaps for historical reasons thinking that Holocaust victims were somehow complicit in their abuse. It made me realise that this poor attitude is alive in Scottish society today.

"It did make me question my own credentials for doing this, and spoke about my doubts with a Rabbi. She said I must do these paintings, and when I asked her why she said it was precisely because I am not Jewish that I should do them."

And that, by anyone's reckoning, is nothing to smile about.

�¢ Forgetfulness: The Holocaust and Beyond, an exhibition of paintings by Roy Petrie, is at the not-for-profit iota Gallery, Unlimited Studios, 25 Hyndland Street, Glasgow G11 5QE from today until January 31 (unlimitedstudios.co.uk). The paintings are not for sale.