Angela Rayner is pressing ahead with plans to replace Sir Keir Starmer as Labour leader and Prime Minister. The former Deputy Prime Minister has raised £1 million to pay for a leadership campaign and launched a "charm offensive" to win over potential donors, it was reported. An ally said: "She has received more than a million in firm pledges and is ready to go", the Mail on Sunday reported.

She has also started promising Cabinet jobs to her supporters among Labour MPs, to ensure they have an incentive to back her bid for the top job. In addition, Ms Rayner has set up a new business called The Office of Angela Rayner Ltd, to help organise any campaign. She has raised the cash amid growing speculation that Sir Keir could quit, or be forced out by Labour colleagues, following local elections in May if his party suffers heavy defeats in votes for the Scottish Parliament, Welsh Parliament and English local councils.

Labour also fears losing the Gorton and Denton by-election on February 26, after Greater Manchester Mayor Andy Burnham was barred from standing.

One obstacle facing Ms Rayner is the ongoing HMRC's investigation into the tax row which forced her to resign from the Cabine last year, after she admitted underpaying stamp duty on a £800,000 flat in Hove. She is said to be keen for the inquiry to be concluded.

But Ms Rayner is not the only threat to Sir Keir's leadership. The attempt to block Andy Burnham's return to Parliament has only made the mayor, who previously served as an MP and Cabine Minister, even more determined according to reports.

One Burnham supporter said: "The blocking has only delayed the inevitable. After the impending disaster of May's local elections, the clamour for Andy's return will become irresistible."

Health Secretary Wes Streeting is also said to be "wargaming" plans for a challenge.

Under Labour Party rules, 81 MPs calling for a change of leader would be enough to trigger a challenge - and all three of the potential contenders are understood to have enough supporters to do this.

All three of the main leadership contenders claim to have the backing of the 81 MPs required to trigger a challenge, with Mr Burnham's supporters putting the number at over 100 and Mr Streeting's at more than 200.

Labour has named local councillor Angeliki Stogia as the party's candidate in the Greater Manchester by-election.

But Sir Keir has not made any commitment to visit the seat to campaign - amid fears that he would be "toxic" to local voters.