Labour leadership frontrunner Jeremy Corbyn has warned senior party figures they are underestimating the "huge levels of public support" for his campaign as the contest becomes increasingly acrimonious.
The radical left-winger dismissed claims that he did not want to be prime minister, insisting his "serious" pitch for the top job was the "greatest opportunity" for the party to win back voters who have turned to the Conservatives and Ukip.
Mr Corbyn's two main rivals, Andy Burnham and Yvette Cooper, have been engaged in a bitter fight over who is best placed to stop the backbencher's rise, with both camps demanding the other clear the way.
Mr Burnham has tried to win over Mr Corbyn's supporters by insisting they share "common ground" and suggested that the Islington North MP did not want to take the party all the way to No 10.
Talking to supporters in central London, Mr Corbyn laughed off claims he did not want to be prime minister.
He said: "Why would I be here, why would our campaign be here, if we didn't want to win this campaign, in order to make the Labour Party a more effective campaigning organisation, in order that we can win the 2020 election?
"I heard Andy's comments. I didn't spill my coffee at the time. I smiled."
Mocking apparent plots among opponents to prevent him from winning the contest, he went on: "I do not think anyone should pull out. They have been nominated, they are valid candidates. We have some more hustings coming up, we will continue the debate.
"If others want to debate arcane procedures that's up to them.
"We are in this campaign because we are serious. We are in this campaign because we have huge levels of public support."
He accused prominent internal critics - including former party leaders Lord Kinnock, Tony Blair and Gordon Brown - of failing properly to read his policies or understand their appeal.
"This is the greatest opportunity the Labour Party has ever had to reconnect with people across this country, to bring people back who were seduced into voting Tory or Ukip because they didn't see us offering a real alternative.
"There are some members of the Parliamentary Labour Party who don't necessarily agree with everything I say.
"I invite the Parliamentary Labour Party to understand that there is a huge democratic movement in this country which is getting great resonance with older people coming back to Labour and younger people who were turned off by yah-boo-sucks abusive politics coming into it for the first time. Let's be happy - things are going well."
Mr Burnham has warned it would be harder to unite the party following the leadership contest if "bad blood" and "negativity" were allowed to take over.
He told BBC Radio 4's Today programme: "If we let this bad blood as you describe it, the negativity, take over, this party will be harder to unite coming out of this contest and that is what I am focused on.
"I want to win this contest and then unite this party."
Referring to warnings that Labour may be reduced to a party of angry protest under Mr Corbyn, Mr Burnham said: "People may be overstating their criticisms, people don't know that."
He said: "This party needs to unite coming out of this race and I think some of the language now needs to be considered, more considered than it is, because if you fuel this negativity and these warnings you just push these two camps apart."