Labour leadership candidate Jeremy Corbyn made a final bid to get on the ballot paper with a characteristically left-wing call for the party to represent its supporters' "gut feelings" on nuclear weapons and human rights.
Mr Corbyn revealed he now has the backing of 22 MPs, 13 short of the 35 needed to get on to the ballot paper before nominations close tomorrow.
The leadership contest is currently a three-horse race, with Andy Burnham, Yvette Cooper and Liz Kendall getting the required support.
But senior party figures Lord Prescott and Frank Field urged MPs to back Mr Corbyn to broaden the terms of the debate, even if they do not agree with his views.
The Islington North MP is standing on a staunchly left-wing position, opposing cuts and calling for the scrapping of the Trident nuclear deterrent.
Mr Corbyn told Sky News's Murnaghan programme: "What I'm trying to do is to say there is a Labour tradition here, a Labour tradition of public enterprise, of public ownership, a Labour tradition of investment in social, health services, which I think is a very strong one and what brings a lot of people into the party and brings a lot of people to vote for us in the first place.
"I want to raise those issues, I also want to raise the issues of nuclear weapons, of Trident, of human rights and justice, just to say to everyone in the party - there are a lot of people out there who actually want the Labour Party to represent what they, in their gut feelings, are all about.
"I'm not looking for this for some personal aggrandisement, I'm much too old for that kind of thing, I'm doing this because I want there to be a serious debate in the party in which those points of view are heard, are put, are debated."
Former deputy prime minister Lord Prescott said it is important for the "soul of the party" that Labour members are allowed to vote on Mr Corbyn's platform.
Writing in the Sunday Mirror, he said: "I may not agree with a lot that left-winger Jeremy Corbyn says. But it's important in this debate for the soul of the party that members get to vote on his views.
"That's why I hope Labour MPs lend Corbyn their votes to get them on the leadership ballot. Likewise in the deputy leadership election, I'd like to see campaigners like Stella Creasy put their case to members."
Meanwhile, Mr Field said it should be easier for Labour MPs to oust the party leader if it is clear they could cost them victory at an election.
Revealing he had tried to spearhead moves to replace both Gordon Brown and Ed Miliband, Mr Field said Labour should introduce a similar system to the Tories, which would allow 30 MPs to trigger a vote of confidence in the party leader.
The former welfare minister also raised the possibility of David Miliband becoming leader before 2020, saying the idea "could gain traction as the next election nears".
Writing in the Mail on Sunday, Mr Field said: "We, like the Conservatives, must build into our parliamentary rules a trapdoor mechanism through which leaders likely to fail can be quickly dropped.
"This is why I've written to eight senior fellow Labour MPs asking them to back a change in the Parliamentary Labour Party's rulebook which would give us a similar despatching policy as the Tories have.
"Jim Fitzpatrick, Paul Flynn, Roger Godsiff, Margaret Hodge, George Howarth, John Mann, Siobhain McDonagh, Barry Sheerman and I are asking if John Cryer, the Parliamentary Labour Party chairman, would change our rules so that if he received, say, 30 signed letters from Labour MPs asking him to call a vote of confidence in the leader, such a vote would have to be put. Who signs the letters should remain anonymous until that debate takes place.
"Of course I hope that whoever wins the current Labour leadership contest does well, and that this mechanism will never have to be used.
"But this safety-valve would increase our future chances of winning elections. Westminster is rife with rumours that David Miliband wants to come back. I am not sure I would support such a move at present, but it could gain traction as the next election nears."