A Labour MP has insisted that Ed Miliband would never agree to scrap Trident to become Prime Minister.
The SNP has made abolishing the nuclear deterrent on the Clyde a pre-requisite for any deal to prop up a minority Labour government after the general election.
But Barrow and Furness MP John Woodcock said Mr Miliband would never agree to such a condition.
Polls suggest that the SNP, alongside other smaller parties, could potentially hold the balance of power at Westminster in May.
The nationalists have already ruled out a coalition with the Conservatives, but have suggested that they could reach an agreement with Labour, if the party agreed to certain concessions.
Mr Woodcock said: "I think we have to call (the SNP) out on (this) because no Labour government will deal on this.
"We will not put the future nuclear security of future generations at risk for any kind of deal with the nationalists."
He added: "I understand that Ed Miliband is not going to start saying 'this is my red line and that is my red line' because we are campaigning for a Labour majority and, frankly, once you say one thing everything is on the table.
"So I understand from his perspective why he's not going to say those words.
"But all all of us are absolutely clear that this is not going to be part of any deal, it would be deeply irresponsible to do it and we're not going to do it.
"It's not going to happen. Ed as future Labour Prime Minister will not make that deal."
Angus Robertson, the SNP's defence spokesman and Westminster leader, said that Mr Woodcock's comments clarify "what we already know - Labour want to renew the arsenal of Trident nuclear weapons dumped on the Clyde."
He added: "It's no wonder Labour are losing their way in Scotland as the SNP sees its highest ever levels of support."
"People in Scotland know that they can trust the SNP to stand up for their interests at Westminster."
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