Liz Kendall has called for a voting pact with Andy Burnham and Yvette Cooper, her rivals for the Labour leadership, in an attempt to stop the left-wing front-runner Jeremy Corbyn winning the race.

In an interview with The Independent, Ms Kendall urged her supporters to vote for only three of the four candidates and to mark either Mr Burnham or Ms Cooper as their second and third preferences. She asked them not to give any of their votes to Mr Corbyn.

Under Labour’s preferential voting system, if no candidate wins more than 50 per cent of the votes, the bottom one drops out and the second preferences of their backers are reallocated. With Mr Corbyn set to benefit most from a last-minute surge of recruits that will give more than 600,000 people a vote, an anti-Corbyn alliance by the three mainstream candidates is now seen as the only way to stop him pulling off a remarkable victory on 12 September. The first ballot papers will be sent out today.

Moderate Labour MPs expressed concern that as leader, Mr Corbyn would force them to vote for his left-wing agenda in the Commons after he outlined plans to give party members more influence over policy. MPs fear they could be deselected before the 2020 election if they do not toe the line.

Ms Kendall said: “I will be using my second and third preferences….It won’t be for Jeremy. I will be strongly urging all of those who are putting me as their first preferences to use their second and third preferences.”

Polls show the Blairite candidate in fourth place but voting choices of her backers could prove important. “It is really important that people use three preference votes,” said Ms Kendall. “I have set out very clearly where I differ with all the candidates but our differences with Jeremy’s kind of politics are far greater.”

Ms Kendall will not reveal whether she will make Mr Burnham or Ms Cooper her second choice. “The main thing people need to consider is who is the best placed person to win against Jeremy,” she said.

However, some of Ms Kendall’s prominent backers will make Mr Burnham their second preference. There has been tension between the Kendall and Cooper camps, with Ms Cooper’s team accused of drawing attention to Ms Kendall being childless and accusing her of “swallowing the Tory manifesto.”

John Woodcock, an MP and senior member of the Kendall team, told his Barrow and Furness party members in a letter: “After giving it much thought, I have decided to give my second choice to Andy Burnham and third to Yvette Cooper. It was a difficult decision because I think that Yvette is a strong candidate….Most importantly though, I think Andy is the candidate who has the best chance of finishing ahead of Jeremy Corbyn.”

Gloria de Piero, the shadow Equalities Minister, and backbencher Simon Danczuk, who are backing Ms Kendall, will also name Mr Burnham as their second preference.

But some Kendall supporters will opt for Ms Cooper as their number two and put Mr Burnham as number three. They include Tristram Hunt, the shadow Education Secretary, who has told his party members in Stoke-on-Trent: “I will not be awarding any of my preferences to Jeremy Corbyn.” Mr Hunt admitted there was “obvious popular enthusiasm for him in some parts of the movement,” but said his leadership could pose a “very real risk” to the party’s future.

Ms Kendall’s move was welcomed by Ms Cooper’s team, who insist their candidate has the best chance of overtaking Mr Corbyn. But the Burnham camp reacted coolly. It is convinced that it is in second place and capable of winning without organised tactical voting.

There is growing tension between the Burnham and Cooper teams as they battle to become the “stop Corbyn” candidate. After Mr Burnham criticised Ms Cooper for a fighting speech in which she tackled “Corbynmania” head on, her allies accused Mr Burnham of “pandering to Corbyn” and ignoring the vital task of taking votes away from him to stop him winning a knockout victory with more than 50 per cent of the votes.

Ms Cooper won praise for a powerful speech in Manchester in which she said Mr Corbyn offered “old solutions to old problems.” Describing his politics as “subversive”, she claimed his policies were neither credible nor radical. She told her audience: “So tell me what you think is more radical. Bringing back Clause IV, spending billions of pounds we haven’t got switching control of some power stations from a group of white middle-aged men in an energy company to a group of white middle-aged men in Whitehall, as Jeremy wants? Or extending SureStart, giving mothers the power and confidence to transform their own lives and transform their children’s lives for years to come?”

The shadow Home Secretary declared: "We can't just luxuriate in our own righteousness out on the sidelines. That's not a luxury the most vulnerable in Britain can afford. It's not enough to be angry at the world. We're the Labour Party, we have a responsibility to change the world or what's the point of us at all?"

Labour leadership: The Contenders Show all 4 1 /4 Labour leadership: The Contenders Labour leadership: The Contenders Jeremy Corbyn Jeremy Corbyn started off as the rank outsider in the race to replace Ed Miliband and admitted he was only standing to ensure the left of the party was given a voice in the contest. But the Islington North MP, who first entered Parliament in 1983, is now the firm favourite to be elected Labour leader on September 12 after a surge in left-wing supporters signing up for a vote. PA Labour leadership: The Contenders Liz Kendall Liz Kendall has been labelled the Blairite candidate throughout the contest, which partly explains why she has failed to attract the support needed in a party that has drifted even further from the centre-ground of British politics since the election. She has faced criticism over her relative lack of experience, having only served as an MP since 2010 and having no experience of ministerial or shadow cabinet roles. But that very lack of experience allowed her to initially make a pitch as the only candidate offering real change and a real break from the Blair/Brown/Miliband years, until Jeremy Corbyn entered the race and shifted the whole debate to the left. She is set to finish a disappointing fourth. PA Labour leadership: The Contenders Andy Burnham Andy Burnham started out as the front-runner in the leadership election, seen as the candidate of the left until Jeremy Corbyn entered the race. The former Cabinet minister has found himself squeezed between the growing populism of Corbyn’s radical agenda and the moderate, centre-left Yvette Cooper, not knowing which way to turn. It has attracted damaging labels such as ‘flip-flop Andy’, most notably over his response to the Government’s Welfare Bill. He remains hopeful he can win enough second preference votes to take him over the 50 per cent threshold ahead of Corbyn. PA Labour leadership: The Contenders Yvette Cooper.jpg Yvette Cooper has put her experience and achievements in government at the heart of her offer to the Labour party. She played a key part in setting up Sure Start in Tony Blair’s government and has pledged to continue her record on delivering for young families by promising a “revolution in the way families are supported” by introducing universal free childcare. She has also championed her role as a full-time working mother, taking pride in telling audiences that she does the school run for the kids before her day starts as a politician. But she has been criticised for being too wooden and lacking in passion and her attacks on Liz Kendall for “swallowing the Tory manifesto” at the start of the leadership contest have been criticised for helping Jeremy Corbyn brand all three mainstream candidates as ‘Tory-lite’. PA

But Mr Burnham refused to join the criticism, saying those attacking Mr Corbyn were “misreading the mood of the party.” He pledged: “I will be keeping it positive.”