The move is the first step in a shake-up of Labour’s top team by Sir Keir after he promised changes in response to the “super Thursday” bloodbath.
Ms Rayner, the deputy leader, has been criticised by some MPs for her stewardship of the campaign in the largest round of ballot outside a general election for many years.
But her removal threatens to escalate a civil war over the future of the party in the wake of the defeat in the Hartlepool by-election — a town held since the 1960s — to Conservatives and the loss of more than 225 councillors.
“Keir said he was taking full responsibility for the result of the elections - and he said we need to change,” a Labour source said.
“That means change how we run our campaigns in the future. Angela will continue to play a senior role in Keir’s team.”
It is understood that Ms Rayner will be offered another senior position within Sir Keir’s team, but her office declined to comment, fuelling speculation over whether she will accept an alternative role.
She cannot be sacked as deputy leader, as it is a role directly elected by party members. Her predecessor Tom Watson hung on to the job for four years despite being at loggerheads with Jeremy Corbyn.
Two other senior female MPs, Lisa Nandy and Anneliese Dodds, have also been tipped for demotion in what is expected to be a major shadow cabinet reshuffle. One Labour insider told The Independent Ms Nandy may be the “next northern woman to carry the can”.
The move to sack Ms Rayner from the role as party chair and national campaign coordinator has led to accusations that Sir Keir is “scapegoating” the senior MP, blaming Labour’s dismal showing on his failure to offer voters a compelling vision.
Speaking on Friday, Sir Keir said he was “bitterly disappointed” with the results and vowed to take responsibility and to fix Labour’s election woes.
Seizing on the comments, former shadow chancellor, John McDonnell, said: “Keir Starmer said yesterday he took full responsibility for the election result in Hartlepool and other losses. Instead today he’s scapegoating everyone apart from himself. This isn’t leadership it’s cowardly avoidance of responsibility.”
Co-chair of the left-wing organisation Momentum, Gaya Sriskanthan, echoed the view, saying: “Angela Rayner’s sacking is blatant scapegoating.
“It is his failed strategy that has brought us to this point, and he said he would take responsibility. Yet again he has gone back on his word.”
Speaking to Sky News on Saturday evening, Wes Streeting, a member of the Labour frontbench, said he hadn’t heard anything officially from the party regarding Ms Rayner being sacked from the roles.
“Angela Rayner is the deputy leader of the Labour Party, she’s not going anywhere, she’s a formidable campaigner, socks it to the Tories,” he said.
As well as the shock defeat in Hartlepool, Labour had a net loss of six councils and more than 200 seats in the local elections, losing control of the likes of Harrow, Essex, and Plymouth local authorities in the process.
The party also failed to topple Tory mayoral incumbents in the Tees Valley and the West Midlands, although did produce a surprise victory in the West of England mayoral contest and the Cambridgeshire & Peterborough race.
One bright spot for Labour was the overwhelming first-round victory in the vote for Greater Manchester mayor for Andy Burnham, who did little to quell speculation that he is jockeying for position in an eventual leadership contest.
“In the distant future, you know, if the party were ever to kind of feel that it needed me, well I’m here and they should get in touch,” he told Sky News
Mr Burnham said that there had to be “substantial change in the way the Labour Party is working”.
He said: “They have lost an emotional connection with parts of the country that is going to take a lot of work to get back.
“I think the party has to do a lot of soul-searching about these results and understand why we’ve done well in places like Wales, places like Greater Manchester, and it really needs to then buy into English devolution and build from the bottom up.
“That’s what these results are telling them.”