Jeremy Corbyn is "hiding behind a closed door" over calls for him to step down, his rival Angela Eagle has said ahead of her Labour leadership bid.
Ms Eagle, who recently quit as shadow business secretary, insisted her bid to take over the party and oust Mr Corbyn is about uniting Labour, not splitting it.
The Labour leader said he was "disappointed" that she was poised to challenge him and said he will fight for the leadership.
Speaking to ITV's Peston on Sunday, Ms Eagle said: "I don't think he's been able to communicate with the electorate and he's now lost the confidence of the parliamentary (Labour) party.
"Tom Watson, our deputy leader who's got his own mandate, Rosie Winterton, the chief whip, John Cryer, who's chair of the Parliamentary Labour Party and a friend of Jeremy's, have all been trying to get him to recognise that he cannot continue in the job because he's lost confidence of the PLP.
"He's hiding behind a closed door, denying that this is a fact. That's not leadership."
Predicting an early election, she added: "There could easily be a very quick general election and I believe I'm the right person to lead the Labour Party into that general election."
But the Labour leader urged Ms Eagle, who was the most senior member of his shadow cabinet to quit in protest during the recent turmoil, to "think for a moment" about her actions.
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On BBC One's Andrew Marr Show Mr Corbyn said he had "reached out in a way no other leader has" in an attempt to unite all parts of the party.
Mr Corbyn said he expected to be on the ballot paper as the incumbent leader - an assertion disputed by his opponents.
"I'm expecting to be on the ballot paper because the rules of the party indicate that the existing leader, if challenged, should be on the ballot paper anyway," he said.
Responding to Ms Eagle's decision to launch a challenge, he said: "I'm disappointed, but obviously she is free to do that if she wishes to.
"We have worked together in the past nine months in the shadow cabinet and this is an opportunity when we could be putting enormous pressure on this Tory government."
Mr Corbyn said he had "reached out in a way no other leader has" in an attempt to unite all parts of the party.
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He added: "This is the opportunity for the party to unite against what the Tories are doing, to put forward an agenda which is different to the austerity agenda being put forward by the Tories and actually gain a lot of ground.
"We now have a very large membership, over half a million people are members of our party.
"They have joined for a reason and they want to see a party that is active all the time opposing what this Government is doing."
But in an attack on Mr Corbyn's time as leader, Ms Eagle said: "Jeremy lost us local councillors in the elections, we have failed to win the EU referendum which is going to cause enormous stress and pressure in our country, that is not the leadership that will take us forward.
"I tried over nine months to support Jeremy and his leadership.
"He's not a bad man. He's not a leader though."
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Repeatedly asked whether Mr Corbyn should be allowed to stand in a new leadership contest, Ms Eagle said: "It's fine whoever my opponent is.
"The rules are the Labour Party rules, the National Executive Committee will actually decide when they meet once a challenge is launched on Monday.
"I am concentrating on setting out my vision for our party and our country."
Mr Corbyn said he would be prepared to mount a legal challenge if he was not on the leadership ballot.
"I will challenge that if that is the view they take," he said.
"I would just ask anyone in the party to think for a moment, is it really right that the members of the party should be denied a decision, a discussion, a choice in this? Half a million people are members of the party because they want the party to succeed.
"Surely, they are the people that knock on doors, they are the people that deliver leaflets, they are the people that raise the money."
Mr Corbyn said it would be "irresponsible" for him to quit because of the mandate he had been given by members, and insisted there had been no "wobble" over his leadership.
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He said: "If at the end of the day an election, somewhere, results in a different leader, so be it. But I would be irresponsible if I walked away from a mandate that I was given and a responsibility that I was given.
"I ask colleagues to respect that as well."
He added: "There's no wobbles, there's no stress, there's no depression".
Asked if a victory for the Labour left was more important to him than success at a general election, he said: "What's most important is to change the way politics is done in this country, to excite young people and older people into the idea that we can have a society that doesn't divide people, that doesn't have grotesque levels of inequality and we don't make the younger generation worse off than this generation and their children worse off than us."
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He dismissed suggestions from former shadow cabinet minister Owen Smith, who is thought to be considering his own leadership bid, that he would split the party.
Mr Corbyn said: "I joined the Labour Party when I was 16, I've been in the Labour Party all my life" and added "I have no idea why Owen should say such a thing".
Mr Smith said at a meeting with Mr Corbyn he asked him three times whether he was prepared to see a split but "he offered no answer", while the leader's ally and shadow chancellor John McDonnell "shrugged his shoulders and said 'if that's what it takes'."
Mr Smith said: "I am not prepared to stand by and see our party split. And I have asked to meet with Jeremy again tomorrow to see how we can stop that."
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