Labour leader Jeremy Corbyn is facing a full scale revolt by his top team as a string of shadow ministers quit in protest at his leadership during the EU referendum campaign.
Shadow health secretary Heidi Alexander, shadow minister for young people Gloria De Piero and shadow Scottish secretary Ian Murray have all resigned.
Labour sources said shadow transport secretary Lilian Greenwood, shadow Commons leader Chris Bryant and shadow environment secretary Kerry McCarthy are among a group of at least 10 members of Labour's top team who are expected to follow.
The walkouts were triggered by the sacking overnight of shadow foreign secretary Hilary Benn amid reports that he was working to co-ordinate a coup against Mr Corbyn.
Shadow chancellor John McDonnell, one of Mr Corbyn's closest allies, insisted the leader has no intention of bowing to the demands to go.
"Jeremy's not going anywhere," he told the BBC's Sunday Politics.
"He was elected nine months ago, the biggest mandate of any political leader in our country, and he is not going anywhere."
But rebel MPs warned that Mr Corbyn would be unable to form a new shadow ministerial team if he tries to struggle on.
Ms Alexander said there are "a fair number" of other senior Labour figures considering their positions.
Asked how many could join her in resigning, she told ITV1's Peston on Sunday: "I think that there are a fair number of people who do feel similarly to me.
"I know a lot of my colleagues will be asking themselves similar questions to the one I've asked myself this morning."