Nicola Sturgeon has branded Boris Johnson "unfit for office" over his use of confrontational language and tactics in the election.
But the claims were dismissed by the Tories who accused Ms Sturgeon of "high-handed preaching and double standards."
The SNP leader spoke out as she hit the campaign trail in the UK's most marginal seat, North East Fife, after the Prime Minister came under fire in Friday night's TV leader's special over claims he had used racist rhetoric in the past, while host Fiona Bruce asked about homophobic abuse.
Ms Sturgeon was campaigning in North East Fife, where the SNP's Stephen Gethins holds a majority of just two over the Liberal Democrats.
“Only a vote for the SNP at this election is a vote to escape Brexit, lock the Tories out of power and put Scotland’s future in Scotland’s hands," Ms Sturgeon said in the seaside town of Leven.
“Scotland voted overwhelmingly to remain in the EU but we still face being dragged out of Europe by a Tory government we didn’t vote for. Boris Johnson simply doesn’t deserve the chance to return to Downing Street as Prime Minister.
“Everything he has done in his short time in the job – including his illegal shutting down of Parliament – shows that. He is taking the Tories further and further to the right, pandering to the worst excesses of Nigel Farage and the Brexit party.
“And his refusal to accept responsibility for his language and his actions – demonstrated so strongly at the Leaders’ Question Time – demonstrates how unfit he is for office. That is why it is vital that at this election we deprive him of the chance to win a majority.
“Only the SNP can beat the Tories here is North-east Fife and across the rest of Scotland, where we are the main challenger in every single seat they hold.
“The SNP is Scotland’s Remain party, and Stephen Gethins has shown what a superb representative he is – both as a local MP here in Fife and as one of the main anti-Brexit voices at Westminster.
“It is people like Stephen that we need to have in the next Parliament to stop Johnson, the Tories and Brexit in its tracks.”
But a spokesman for the Scottish Conservatives dismissed Ms Sturgeon claims.
“This is yet more high-handed preaching from a First Minister who seems to think she can tell Scots what to think, but never listens,” he said.
“Nicola Sturgeon slams Boris Johnson, yet at the same time she is quite happy to usher Jeremy Corbyn into Number Ten – whose Labour party faces numerous accusations of anti-Semitism, and which has failed to respond properly to allegations of bullying in its ranks.”
“Scots can tell Nicola Sturgeon to end the hypocrisy and double-standards by voting Scottish Conservative on December 12th.”