Labour MPs would move to oust Jeremy Corbyn as party leader on the first day after he is elected, Simon Danczuk has said.
Corbyn, the veteran leftwinger, has become the surprise frontrunner in the race to succeed Ed Miliband - much to the horror of those in the centre and on the right of the party.
Danczuk, who has called on the contest to be halted, said Corbyn would not last in office for "about 12 months". Asked on LBC radio if the plotting would begin on "day one", he said: "Yeah, if not before. As soon as the result comes out. People in the PLP [Parliamentary Labour Party] aren't going to put up with it. "
The Rochdale MP, who was also a harsh critic of Ed Miliband, said he would not put up with the "crazy leftwing policies" advocated by Corbyn.
Labour had to extend the deadline for people to register to vote in the leadership contest from midday until 3pm today after its website crashed. Ballot papers will be sent out on Friday and the result will be announced on September 12.
Commenting at the end of registration to participate in the leadership election, Corbyn said today: "The response to the Labour leadership race from party members and supporters, longstanding and new, is proof of the optimism in the possibility of a popular, modern alternative to the Conservative government.
"All of our focus must be on channelling this extraordinary movement towards a united party that is able to find its confidence and defeat the Conservatives in 2020.
"I particularly want to pay tribute to the Labour Party’s staff who have worked so hard to deliver a robust selection system in totally new circumstances. The professionalism and commitment of the party’s staff shows our movement at its best."
The party has seen a surge in the number of people able to vote in its leadership contest since the election.
Some 282,000 party members, 92,000 trade union and other affiliated members are eligible to vote, but members of the general public can cast a ballot by joining Labour as a "registered supporter" for £3, with 70,000 so far signing up.
However some in the party are worried that it is being infiltrated by the hard left who are actually opposed to Labour values.
Around 1,200 members or supporters of another party have already been excluded from voting in the leadership contest, including hundreds who stood against Labour in local or national elections.
They included 214 from the Green Party, 37 from the Trade Unionist and Socialist Coalition, 13 Tories, seven from Ukip and one from the BNP.
On Tuesday a YouGov poll for The Times showed Corbyn now has a staggering 32-point lead over Andy Burnham, his nearest rival.
The left-wing candidate is poised to win in the first round of voting having polled 53 per cent of the vote - a 10 per cent surge on a month ago. Corbyn, who wants Trident scrapped and industries re-nationalised, has pulled well ahead of Burnham on 21 per cent, Yvette Cooper on 18 per cent of the vote, and Liz Kendall with just eight per cent.
YouGov President Peter Kellner has said he would be "astonished" if Corbyn did not win the leadership race but added: "I have seldom released a poll with as much trepidation as I have done this time."
Labour figures from the centre and right of the party have issued repeated warnings that Corbyn will not be able to win a general election.
Alastair Campbell, Tony Blair's former communications director, said a Corbyn victory in the leadership race would lead to "chaos". In a blog post this week he urged Labour members to choose "Anyone but Corbyn" and encouraged people to sign up as a registered supporter for £3.