Nicola Sturgeon has said she is ready to form an alliance with Labour to put Jeremy Corbyn into Downing Street and “lock the Tories out of Government” if there is a hung Parliament.
The price for such a deal would be Labour’s backing for a new independence referendum next year.
Launching the SNP’s election campaign in Edinburgh, Scotland’s First Minister said a hung Parliament would be the best outcome for Scotland as “it gives us significant influence and power”.
On a day when Mr Corbyn said he was proud of his candidates, as one stepped down after using the offensive term Shylock in front of a Jewish councillor, and another stood down after comparing Israel to a child abuser, Ms Sturgeon said she was no fan of the Labour leader “but we have to work with what we have before us”.
She added: ”I would never support a Conservative government, I can’t foresee the SNP being in a formal coalition, but we would look, as we’ve said in the two previous general elections, to form alliances that can keep the Tories out of power.”
She added that the SNP's support for a minority Labour government would come with a significant shopping list of demands, including an end to austerity, social security reform, the devolution of extra powers and greater action from the UK Government on climate change.
She also claimed that Boris Johnson’s refusal to give the Scottish Parliament the necessary powers to hold a new independence vote were “unsustainable”.
He said on a campaign to visit to Scotland on Thursday that he would not hand over the so-called Section 30 powers, even if the SNP win an outright majority in the 2021 Holyrood election.
The Prime Minister vowed to "keep our fantastic United Kingdom together and prevent another referendum next year”.
Ms Sturgeon said Labour’s opposition to another bid to break-up Britain was “crumbling” and Mr Johnson’s position on the issue was not “sensible or serious”.
“Nothing Boris Johnson has said in his short tenure as PM has turned out to be the case, so perhaps that should give us all hope for the future,” she added.
“If you listened to Boris Johnson’s comments yesterday, what he appeared to be saying to Scotland, pretty much in terms, was ‘I don’t care how you vote, however you vote I’m going to ignore you’.
“I would say to the people of Scotland this election is a great opportunity for us to show Boris Johnson to show exactly what we think of such a contemptuous and disrespectful attitude towards Scottish democracy.”
Ms Sturgeon said she expected the PM’s position on a new referendum would have as long a shelf life as his prediction that the UK would leave the EU on October 31 “do or die”.
She claimed a the SNP already had a “cast iron” mandate for a poll and said a vote for the Nationalists was a vote to escape Brexit and "take Scotland's future out of the hands of Boris Johnson and a broken Westminster system”.
The SNP pledged earlier to introduce a Bill to protect the NHS from any future trade deals with foreign nations, including the US.
Ms Sturgeon said: "We will fight tooth and nail any attempt to expose the national health service to a post-Brexit trade deal with Donald Trump.
"That's why after the election, SNP MPs will bring forward a new law - an NHS protection Bill - to explicitly protect the NHS in all four countries of the UK from becoming a bargaining chip in future trade deals.”
Pamela Nash, chief executive of the Scotland in Union campaign, said every vote for the SNP was a vote for "more division and economic chaos", adding: "Scotland’s future is already in Scotland’s hands, and we have chosen a better future as part of the UK – with more and more former Yes voters now choosing to remain in the UK.
“The best future for Scotland is to remain in the UK, saving the pound, avoiding a hard border with England, and maintaining the bonds between friends, families and neighbours across the UK.”