Ed Miliband has resigned at Labour leader after a disastrous performance for his party in the General Election.
Miliband biographer and former HuffPost UK political director Mehdi Hasan tweeted the next leadership contest can't be a repeat of the long 2010 contest.
There's no way the next Labour leadership contest will take 3 and a half months like the last one did.May 8, 2015
Newsnight reporter Laura Kuenssberg cited a Labour source saying the party wanted a leadership contest "asap".
Another Labour source - 'they want Ed M gone by Monday and a blood letting leadership battle asap'— Laura Kuenssberg (@bbclaurak) May 8, 2015
Ed Miliband took "absolute and total responsibility" for the election result in his resignation speech: "I am so sorry for all of those colleagues who lost their seats - Ed Balls, Jim Murphy, Margaret Curran, Douglas Alexander and all the MPs and indeed candidates who were defeated.
"They're friends, colleagues and standard bearers for our party, they always have been and they always will be."
He continued: "Britain needs a strong Labour Party. Britain needs a Labour Party that can rebuild after this defeat so we can have a government that stands up for working people again.
"And now it's time for someone else to take forward the leadership of this party.
"So I am tendering my resignation, taking effect after this afternoon's commemoration of VE Day at the Cenotaph.
"I want to do so straight away because the party needs to have an open and honest debate about the right way forward without constraint."
Below are the most likely candidates to try and succeed Miliband.
Ed Miliband arrives at Labour HQ
GENERAL ELECTION 2015