Polls suggest the SNP is on track to take seats from Labour north of the border raising the prospect that a deal with the nationalists might be the only way Ed Miliband can form a Government after May 7.
The Prime Minister has suggested such an alliance would put the future of the Union under fresh threat and challenged Labour to explicity rule out coalition with the SNP.
Speaking on the Andrew Marr Show, Labour’s Shadow Energy Secretary and Don Valley MP Caroline Flint said: “She told The Andrew Marr Show: “We are focused on winning a Labour majority government. Let me say this. We do not want, we do not need and we do not plan to have any coalition with the SNP.
“There is going to be a choice at this election between who will sit in Number 10. It is a choice between Labour or the Conservatives forming a majority government.
“Every vote that is cast for the SNP makes it more likely that David Cameron will retain the keys to Number 10.
“The SNP is not the social conscience of the Labour party. They might like to see themselves like that but they are not.”
Labour’s deputy leader Harriet Harman said the question was being pushed by Mr Cameron to deflect attention from the Conservatives.
SNP leader Nicola Sturgeon has described a formal coalition as “unlikely” but hinted that nationalist MPs could support a minority Labour government to pass measures on an issue-by-issue basis.