Media playback is unsupported on your device Media caption Liz Kendall: "I'll be fighting for what I believe in till the very end"

Labour leadership contender Liz Kendall has dismissed calls for her to pull out of the contest and back another candidate to defeat Jeremy Corbyn.

It follows a YouGov poll for the Times putting left-winger Mr Corbyn ahead in the race and Ms Kendall fourth.

But she said: "I'll be fighting for what I believe in until the very end."

Ex-minister Alan Milburn followed Tony Blair in warning against a victory for Mr Corbyn - while ex-deputy PM Lord Prescott told the party to "calm down".

Mr Milburn told the BBC the party would only win the next election if it occupied the centre ground.

He added: "The alternative is that Labour lurches to the left. If it does that, frankly, it has a death wish."

'Don't leave it to the boys'

Norman Smith, BBC assistant political editor, said pressure had been mounting on Ms Kendall to withdraw from the race.

But the Leicester West MP rejected that idea in a BBC interview - after her aides had accused Andy Burnham's and Yvette Cooper's camps of "fuelling" the idea.

One source said: "Both Andy and Yvette have seen their numbers fall this week following the flip flop over welfare and that's what is making these campaigns try and make Liz somehow the problem to distract from their own issues."

The source said that under the preference voting system it would not make any difference, even if Ms Kendall pulled out.

Ms Kendall said she had always been an outsider in the race but said there were 51 days left to get people's support.

She said a victory for Mr Corbyn would be a "disaster", saying that turning back to the politics of the 1980s and losing elections "does nothing to help the people" the party wants to help.

Ms Kendall added that she was the only candidate offering an alternative to the politics which lost the party the last two elections, saying her policies would help Labour win power "so we can change the country for the better".

Labour leadership contest

Image copyright Getty Images Image caption Liz Kendall has been urged to back Andy Burnham or Yvette Cooper to defeat Jeremy Corbyn

Who are the candidates? Andy Burnham, Yvette Cooper, Jeremy Corbyn, Liz Kendall

Andy Burnham, Yvette Cooper, Jeremy Corbyn, Liz Kendall Dates: Ballot papers will be sent out on 14 August; voting can take place by post or online. They must be returned by 10 September. The result is on 12 September.

Ballot papers will be sent out on 14 August; voting can take place by post or online. They must be returned by 10 September. The result is on 12 September. Who can vote? All party members, registered supporters and affiliated supporters - including those joining via a union - get a vote

All party members, registered supporters and affiliated supporters - including those joining via a union - get a vote What is the voting system? The Alternative Vote system is being used so voters are asked to rank candidates in order of preference

The Alternative Vote system is being used so voters are asked to rank candidates in order of preference How does it work? If no candidate gets 50% of all votes cast, the candidate in fourth place is eliminated. Their second preference votes are then redistributed among the remaining three. If no-one has still not got 50% of votes the third place candidate is eliminated with their second preferences (or third in the case of votes transferred from the fourth place candidates) redistributed. It is then a straight head-to-head between the last two candidates with the one having the most votes winning.

At-a-glance profiles of the four contenders

Earlier, speaking to BBC Radio 4's Today programme, Ms Cooper said Ms Kendall should "certainly not" withdraw from the contest and "leave it to the boys, just because of one poll".

The Labour leadership race has been the subject of widespread debate after a YouGov poll this week suggested that in the final round of voting Mr Corbyn could finish six points ahead of bookmakers' favourite Mr Burnham.

The poll suggested Mr Corbyn could receive 43% of first preference votes, ahead of Mr Burnham on 26%, Ms Cooper on 20% and Ms Kendall on 11%.

Taking second preferences into account, the poll - of 1,054 people eligible to vote in the contest and carried out between Friday and Tuesday - pointed to a 6% victory for Mr Corbyn.

Labour MP Frank Field, one of the MPs who "lent" Mr Corbyn his nomination, said the debate "hasn't been widened" by his candidacy, and the other candidates needed to up their game to defeat him.

"I hope that in this whole process at least one of the candidates who say they oppose Jeremy has actually got both the physical courage and the intellectual clout to start that debate.

"If not goodness knows what position we will be in after the votes are counted," he told BBC Radio 4's World at One.

'A terrible legacy'

Speaking to the Times, Lord Mandelson warned the Labour Party's existence as "an electoral force" was at stake.

"Those of us who stayed and fought to save the Labour Party in the 1980s will be experiencing a growing sense of deja vu," he told the Times.

"The last five years have left us with a terrible legacy to overcome with the existence of the Labour Party as an effective electoral force now at stake."

On Tuesday, former prime minister Mr Blair warned Labour would not win again from a "traditional leftist platform".

Image caption Lord Mandelson has warned Labour's electoral existence is at stake

And former adviser to Mr Blair, John McTernan, told BBC Newsnight two of the candidates should withdraw in favour of an "anyone but Corbyn" candidate.

Former deputy leader Lord Prescott told BBC Radio 4's Today programme Mr Blair had been wrong to "abuse" supporters of Mr Corbyn with his "transplant" comment.

He also said acting leader Harriet Harman had overstepped her authority in setting out Labour's support for some of the government's welfare cuts.

Lord Prescott, Mr Blair's deputy PM for ten years, added: "Who the hell is John McTernan?"

He said it would not be a disaster if Jeremy Corbyn won, but said he would not be voting for him, adding: "It's the party's decision not the MPs'."

Labour is due to announce its new leader at a special conference on 12 September.