Angela Rayner has told Labour MPs the time to oust Keir Starmer from No 10 is ‘now or never’ as the Prime Minister faces a critical week in his fight for political survival.

With the former Deputy Prime Minister now the frontrunner to succeed the embattled Sir Keir if he is toppled, backbenchers claimed that Ms Rayner and her allies were spending the weekend canvassing support among her colleagues. 

One MP said: ‘The line from Angela is that it needs to happen now otherwise this deadly stalemate will drag on forever. That it’s now or never.’

Sir Keir could face a critical Commons vote on his future on Tuesday. Speaker Sir Lindsay Hoyle is considering whether to grant opposition parties a vote on whether to refer the PM to the privileges committee for a ‘sleaze inquiry’ into claims he misled the House of Commons about the appointment of Lord Mandelson as ambassador to the US.

If the vote goes ahead, Sir Keir’s allies say it would be treated as an effective confidence measure in the Government. If he lost, he would be finished as Prime Minister.

Ms Rayner and her two main rivals for the leadership, Greater Manchester Mayor Andy Burnham and Health Secretary Wes Streeting, are all now ready to launch campaigns if Sir Keir announces he is standing down as Labour leader on May 8, the day after the local and devolved government elections.

If he does so – either as a result of Cabinet pressure, from a ‘stalking horse’ challenge by an MP such as Armed Forces Minister Al Carns, or of his own volition – they expect him to say that he would stay until the autumn, when a contest would produce a new leader in time for the party’s annual conference.

Ms Rayner is the frontrunner because Mr Burnham – the most popular candidate both inside the party and among the country at large – is still trying to find a way back into the Commons to give him the platform for a leadership bid, while Mr Streeting is regarded as ‘too Blairite’ by most voting party members.

It had been thought that Ms Rayner would not launch a bid until her controversial tax affairs had been settled. But her allies think she will soon be either exonerated or found to have committed a minor technical breach for underpaying stamp duty on her seaside flat in Hove.

One said: ‘Ideally she wanted to wait for the tax issue to be sorted. But she came to the view that if it all kicked off she’d have to throw her hat in the ring. And it’s all kicking off.’

Another source said that Ms Rayner was ‘over the moon’ to be close to an agreement with HMRC.

A source close to Ms Rayner said that ‘this is obviously untrue’ in relation to the ‘now or never’ comment.

But a Labour MP said: ‘Ange’s line is that Burnham has no quick way back in [to the Commons] so it has got to be her’.

To mount a bid for the leadership, candidates need the backing of 81 MPs. Mr Burnham’s allies say he is still considering routes back in to Parliament, but is conscious that it could all move ‘very quickly’. He has been in discussions with Ms Rayner about a potential ‘dream ticket’, but his supporters say they remain unclear about the former Deputy PM’s intentions.

Other potential leadership contenders include Energy Secretary Ed Miliband and Foreign Secretary Yvette Cooper, who is being touted by friends as a ‘caretaker PM’ for a year.

The proposed sleaze vote on Sir Keir comes after he claimed last week that No 10 had put no pressure ‘whatsoever’ on the Foreign Office over Lord Mandelson’s appointment.

His comments appear to contradict Sir Olly Robbins, the department’s former permanent secretary, who told MPs that Downing Street had exerted ‘constant pressure’ to install the Labour peer in Washington. The vote could be held on the same day Sir Philip Barton, Sir Olly’s predecessor, gives what could be critical evidence to MPs on the scandal.

It was the privileges committee which ended Boris Johnson’s political career after it found that he had lied about lockdown parties.

Ministers and backbench MPs have been discussing options to force out Sir Keir following the local elections, which polls suggest will lead to disastrous losses for Labour. 

A poll of Labour members by Survation found that 46 per cent want a new leader, while 44 per cent think Starmer should remain in post.

Sir Keir summoned his remaining supporters to Chequers on Friday for a meeting which has been dubbed a ‘survival summit’ aimed at fending off imminent leadership challenges.

The last-ditch fightback could include a Cabinet reshuffle in which Chancellor Rachel Reeves loses her job.

Be very afraid, Red Ed could take the keys to No 11

Ed Miliband as Chancellor and Wes Streeting as Foreign Secretary are the likely choices in a future Angela Rayner Cabinet, allies told the Mail on Sunday.

In such a scenario, out would go current Chancellor Rachel Reeves, Foreign Secretary Yvette Cooper and Liz Kendall, the Science Secretary.

Allies of the former Deputy PM tipped Mr Miliband for Chancellor, not because he was ‘Angie’s first choice’ but due to him being hugely popular and influential within the party. 

Ms Rayner’s leadership rival and current Health Secretary Mr Streeting would be offered Foreign Secretary, if only to keep him away from domestic politics.

Labour deputy leader Lucy Powell to Health Secretary, ex-Transport Secretary Louise Haigh to Mr Miliband’s current Energy Security job, close Rayner ally Justin Madders to education and senior Labour MP Meg Hillier to the Cabinet Office are other suggestions.