Scotland would never "forgive" Ed Miliband if he refused to do a deal with the SNP and let David Cameron stay in power because of it, Nicola Sturgeon has said.
The SNP could be the third largest party in parliament after the election - one poll even showed they might win all 59 Scottish seats.
Immediately afterwards, Sturgeon faced questions from a studio audience on BBC Scotland.
Nicola Sturgeon has said she would do a deal with Labour to keep the Tories out of power, regardless of who had the most votes
Sturgeon told them: "I heard Ed Miliband and he sounded awfully like he was saying, and I hope that I am wrong about this because I think people across Scotland and much of the UK will be appalled if I am right, he sounded as if he was saying that he would rather see David Cameron and the Conservatives back in government than actually work with the SNP.
''Now, if he means that then I don't think people in Scotland will ever forgive Labour for allowing the Conservatives back into office."
Sturgeon has repeatedly said she would do a deal with Labour to keep the Tories out of government, even if Labour was no the largest party.
She added: "If the opinion polls in recent days have made anything clear, it is that Scotland has an unrivalled opportunity to make our voice heard at Westminster like never before.
"By uniting as a country - north, south, east and west - to elect a big group of SNP MPs, Scotland gains the decisive position at Westminster needed to ensure that the interests of people across Scotland are not ignored in the way they too often have been in the past.
"Everyone can be part of it, and all of Scotland stands to benefit."
Miliband is due to visit Scotland to plead with people to vote Labour - and attack the nationalists.
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Speaking ahead of his visit, Miliband said: "Remember our great leaders, from Keir Hardie to Jennie Lee, John Smith to Donald Dewar. What would they want today?
"We could be on the verge of electing a Labour government. They would want to be part of it."
He added: "Nationalism never built a school. It never lifted people out of poverty. It never created a welfare state that healed the sick and protected our most vulnerable.
"It is Labour values, Labour ideas and the determination of people across Scotland that has built this country to what it is today."
Scottish Conservative leader Ruth Davidson will join Borders candidate John Lamont at a rally followed by a street stall event in Galashiels.
A Conservative spokesman said: "Ed Miliband is heading to Scotland cap in hand for votes invoking the past not focusing on the future.
"It goes to show that, next Friday, Ed Miliband cannot be Prime Minister without being propped up by the SNP. If you want to stop that happening, vote Conservative on May 7."