Jeremy Corbyn will remain as Labour leader for a "couple of months" into the New Year before handing over to his successor with "dignity", his close ally John McDonnell has said.
Despite pressure for Labour's top duo to quit their posts immediately following the party's bruising general election result on Thursday, the shadow chancellor argued both he and Mr Corbyn should stay for an "interim" period.
However, Mr McDonnell revealed he will leave Labour's shadow cabinet once a new leader is elected to replace Mr Corbyn in early 2020.
"The National Executive Committee officers meet next week, they'll decide the timetable for a leadership election in the New Year," he said.
"It will be the usual time - a couple of months or something like that - so that enables people to have a thorough debate about the election itself, and then choose a new leader.
"Then Jeremy will hand over to that new leader and that's the usual way.
"I think Jeremy will be able to do that with his usual dignity but also - because he's so committed to the party and our movement - he'll be able to enable that debate to happen and then welcome the new leader in, ready in time for us fighting the elections we'll have next May."
He added: "We always have an interim before the new leader is elected, so what better than to put the current team in - because we have a Queen's Speech and a budget by the looks of it as well.
"Use that expertise for the interim period, but also allow the rest of the party to engage in that thorough debate about the future and the new leader."
However, Mr McDonnell ruled out remaining on Labour's front bench beyond Mr Corbyn's departure.
"We'll all go now, the new leader will come in place and appoint their shadow cabinet," he said.
"I won't be part of that shadow cabinet, I've done my bit."
Labour shed 59 seats at the general election from their 2017 election result, as Prime Minister Boris Johnson secured a crushing 80-strong majority.
Mr McDonnell blamed his party's defeat on Brexit and the "horns of that dilemma" that Labour faced in attempting to straddle the Remain/Leave divide.
He also claimed Mr Corbyn - who he described as "one of the most principled, honest, sincere, committed, anti-racist politicians" - was "demonised by a smear campaign" from the media and on social media.
But the shadow chancellor admitted some seats may have been lost by Labour due to "40 years of neglect".
Mr McDonnell has ruled out a leadership bid himself, but namechecked three leading members of Mr Corbyn's shadow cabinet - Angela Rayner, Rebecca Long Bailey and Richard Burgon - as viable contenders.
Meanwhile, shadow foreign secretary Emily Thornberry was tight-lipped on whether she would enter the contest to replace Mr Corbyn, telling reporters that Labour was in "a period of mourning".
"We need to be able to have a chance to stop and think," she said.
Outside of the current Labour shadow cabinet, Wigan MP Lisa Nandy is being urged to run for the leadership.
Former Labour shadow minister Gloria de Piero, who did not stand for re-election on Thursday, posted on Twitter: "No idea what @lisanandy 's plans are but I'd urge her to think about standing to be Labour Leader.
"She represents + is rooted in the communities which suffered terrible defeats. Our party needs to rediscover our heart + our soul. Lisa can do that."
Aberavon MP Stephen Kinnock blamed Labour's defeat on "weak and incompetent leadership", the party's backing for a second EU referendum as a "puppet of the People's Vote campaign", and an election manifesto that was a Christmas "wishlist".
He added: "Corbyn must apologise and resign, we need new leader by Easter."
Neil Coyle, Labour's Bermondsey & Old Southwark MP, accused Mr Corbyn and Mr McDonnell of a "shameless insult to voters" by refusing to depart immediately.
He tweeted: "In 2005 Tony Blair won a third consecutive general election for Labour with a majority of 67. Jeremy Corbyn & John McDonnell called for him to resign.
"In 2019 they helped hand Boris Johnson a majority of 80 & still have not had the decency to go. A shameless insult to voters."
But Mr Corbyn's son Tommy, in a statement on behalf of himself and his two brothers, urged Labour supporters who supported his father's "vision" to "continue the fight".
"To say we are proud is a vast understatement," he said.
"To assume that the ideologies he stands for are now outdated is so wrong. In the coming years we will see that they are more important than ever.
"Thank you to every person who saw his vision and supported it and supported him. From the three proudes sons on the planet, please continue the fight."