ED Miliband has said there will be no Labour government after May 7 if it has to depend on a deal with the SNP.
He suggested he would forego the chance of becoming prime minister if it meant having to rely on an agreement with the Nationalists.
But he left open the option of forming a minority government and challenging other parties to vote against them.
With polls showing the election is likely to result in a hung parliament and a large bloc of SNP MPs, Mr Miliband was asked during a special TV Question Time whether Labour would work with Nicola Sturgeon’s party.
He said he was not prepared to negotiate either a coalition or a confidence and supply arrangement. “If it meant we weren’t going to be in government because we were not having a deal, then so be it.
“I’m not sacrificing the future of this country, the unity of this country, I will not give in to SNP demands about Trident or the deficit or anything like that.”
“I’m not going to have a Labour government if it means deals or coalitions with the Scottish National Party. If the price of Labour government was coalition or a deal with the SNP, it’s not going to happen.”
Asked what he would do if he failed to secure an overall majority, Mr Miliband said: “I am not going to start bartering away my manifesto, whatever the outcome of the election, even if I don’t win a majority.
“We are in a new world in Britain. It was the first coalition that there had been for a long time. But in my view, if we don’t have a majority government it is not about saying go into a darkened room with somebody and start lopping off bits of your manifesto.”
Mr Miliband made his comments during the last UK-wide televised leaders’ event of the election campaign, where the leaders faced audience questions separately after David Cameron refused to take part in a head-to-head debate.
In a follow-up programme, Nicola Sturgeon – who campaigned in the Capital yesterday – said if Mr Miliband wanted a minority government he would have to win support from other parties. “He won’t get his Budget through unless he compromises and listens to other parties.
She said: “It sounded as if he was saying he would rather see the Conservatives back in government than work with the SNP. If he means that, I don’t think the people of Scotland will ever forgive Labour for allowing the Conservatives back into office.”