AN SNP election win will seal a “triple lock” on a second independence referendum and make Westminster resistance “democratically unsustainable”, Nicola Sturgeon has said.

Launching her party’s manifesto in Perth, the First Minister said she already had a mandate based on Brexit, and this had been reinforced by a recent vote in Holyrood.

But she added that if SNP MPs were elected in 30 or more of Scotland’s 59 seats, it would make it impossible for Theresa May to deny Scots a vote on their future after Brexit.

She told activists at a packed Concert Hall in the city: “There is just too much at stake for Brexit simply to be imposed on Scotland, no matter how damaging it turns out to be.

"Our future must be decided by us, not for us.

"Last year's Holyrood election delivered the democratic mandate for Scotland having such a choice and the recent vote of the Scottish Parliament underlined it.

"If the SNP wins a majority of Scottish seats in this election, that will further reinforce our mandate.

“In these circumstances, any continued Tory attempts to block Scotland having a choice, when the time is right and the options are clear, would be democratically unsustainable."

The manifesto said an SNP win would “complete a triple lock” on a referendum.

However Ms Sturgeon twice failed to say how, in practice, she would overcome resistance by a determined Mrs May and a Tory dominated House of Commons.

Despite a narrowing in the opinion polls, Ms Sturgeon’s speech was predicated on Mrs May being returned to power with a large majority of Tory MPs.

That prospect made it vital to vote SNP to give Scotland a strong voice at Westminster, with the party’s MPs standing up to austerity cuts and plans for a hard Brexit, she said.

"We can't afford a Tory government with a free hand to do whatever it likes. We must have strong voices, standing up for our interests and defending the values we hold dear."

The SNP leader barely mentioned Labour, other than warning a vote for Labour on June 8 increased the chance of Tory MPs being elected in Scotland.

She condemned the Conservatives for their "assault on social security", saying it amounted to an attack on the poor, disabled and vulnerable in society.

She said: “These cuts strike at the very heart of how we see ourselves as a nation and our shared ambition for the future. They are unfair and they are designed to divide."

She added: "For the Tories, austerity cuts are not simply a policy response to a particular economic situation. They are political dogma - an ideology."

The SNP’s policies would "restore fairness" to the social security system, she said "Make no mistake - the Tories have sought to undermine faith in the welfare state itself.

"They have set out, deliberately, to stigmatise those on benefits.

"Their rhetoric is cover for the hardship they are causing to those who work hard and struggle to get by on low incomes.

"Children, the elderly, women, the disabled - even the bereaved - are bearing the brunt."

She said the Tories planned another £9bn of social security cuts in the next four years, and while Labour would reverse less than a quarter, SNP MPs would oppose them all.

She said the SNP manifesto offered a “clear alternative to continued austerity", with a plan to free up £118bn more than the Tories would spend over the parliament.

Similar to Labour, she advocated a real living wage of just over £10 an hour by 2022, and the reversal of the two-child cap on tax credits, and with it the so-called “rape clause”, which she called “a policy that shames every Tory candidate who supports it”.

But she was markedly more timid on income tax than Jeremy Corbyn, who has advocated a 45p rate for those earning £80,000 and a 50p rate above £123,000.

Ms Sturgeon said she wanted a 50p rate at £150,000 instead of the present 45p.

She appealed directly to older voters, who are most likely to oppose independence, and said the Tory UK policies on a ‘dementia tax’, winter fuel payments and ending the triple lock on pensions had shown they could not be trusted with safeguarding the elderly, although only the latter would apply in Scotland.

She said: “The Tory manifesto is nothing short of an assault on pensioners.

“[They] think they can take the votes of many older people for granted. If you don't want them to have a free hand to remove your hard-won protections, make sure you elect strong voices who will stand up for you.

"The SNP will protect the winter fuel allowance and with pensioner poverty once again on the rise, we will oppose the removal of the triple lock."

The campaign had revealed the Tories’ “true colours”, she said, adding: “We have a real chance to keep them in check."

Ms Sturgeon announced in March that she wanted to hold a second referendum by spring 2019 to give Scots a choice between Brexit in the UK and pro-EU independence.

However the Prime Minister has ruled out that timescale, saying “Now is not the time”.

The Tory manifesto added further obstacles - saying there could be no vote until there is demonstrable “public consent” for it and only after the Brexit process had “played out”.

Scottish Tory leader Ruth Davidson and Scottish Secretary David Mundell have both suggested the process could run beyond the 2021 Holyrood election, when the Tories hope Holyrood’s pro-independence majority will be replaced by a pro-Union one.

Unlike the SNP’s 2015 and 2016 manifestos, both of which featured a single image of Ms Sturgeon on the front, the new manifesto does not feature the party leader on its cover.

Instead, there are 10 pictures of babies and young children.

Ms Sturgeon denied she was becoming a more divisive figure on the doorstep, adding: “The baby is much cuter than me.”

Ms Davidson said Ms Sturgeon had shown her hand on the constitution: “Nobody is fooled any more. Strip away the bluster and it’s written down in black and white - she wants to drag Scotland back to another referendum by asd early as next autumn.

“That would cost jobs, risk our economy, and distract us all from the real job in hand - improving our schools and public services.

“This was a tired manifesto launch by a First Minister who has failed in this campaign to give people a reason for voting for her party.”

Scottish Labour leader Kezia Dugdale said Ms Sturgeon had confirmed her “number one priority” in the election was “another unwanted and divisive independence referendum”.

She said: “It is clearer than ever that the majority of Scots who don’t want another divisive independence referendum need to send Nicola Sturgeon a message that she should focus on the day job. While Nicola Sturgeon campaigns for independence, standards in our schools have fallen and NHS services face closure.”

Scottish LibDem leader Willie Rennie added: “The SNP must think we are stupid. They barely mentioned independence today but we know independence will be their top priority once the election is over.”