Yvette Cooper and Andy Burnham have comes to blows, both calling for the other to step down from the Labour leadership contest.
Burnham's campaign team accused Cooper of clinging in the race "out of pride" on the day when he pledged to include Corbyn "from the outset" if elected leader.
Cooper's team, meanwhile, said Burnham was "struggling to offer an alternative" to current frontrunner Jeremy Corbyn.
Michael Dugher, the shadow transport secretary and Burnham supporter, told the Guardian: "History will not be kind to those who appear to cling on out of pride when the situation really is quite hopeless."
He added that "the Yvette campaign remains in complete denial as to the fact that they cannot possibly win”.
But Cooper's team said Burnham "needs to step back and leave it to Yvette."
Andy's campaign is struggling to respond to Jeremy which is why he is changing position from day to day.
They claimed the shadow home secretary was best placed to beat Corbyn due to polling data which suggests she is increasingly being selected as second preference and attracting more support in London.
Liam Byrne, a leading supporter of Cooper and shadow universities secretary, told the Guardian that Burnham's camp were "desperate".
"Andy’s team telling the girls to get out of the race is not going to do [him] any favours," he added.
The war of words came after David Miliband, the former 2010 leadership contender, urged party members not to select Corbyn as leader.
The veteran left-winger is the odds-on favourite to win the contest on September 12.
He left a hall in Ealing, West London tonight to address crowds of supporters unable to get in to hear him.