The full scale of the rebellion against Sir Keir Starmer became clear today after MPs who abstained from last night’s vote branded him ‘weak and guilty’.

Ministers tried to play down the revolt by saying Labour MPs who voted for the PM to face a sleaze inquiry over Mandelson were the ‘usual suspects’.

But the PM was rocked after 14 of his MPs sided with the Tories while dozens abstained on a vote for an investigation into whether he lied to Parliament.

Labour whips were dithering over whether to discipline the rebels amid concerns that the PM's position is too weak to boot them out of the party.

One of those who abstained – MP Graham Stringer – said he was unable to support the Government line – though could not back the Tories.

He was joined by three other MPs who said they would have voted in favour of the motion had they been in Parliament.

Mr Stringer told the Daily Mail: ‘The Government response was pathetic – the real issue is there is a disagreement between the PM and other people about whether or not he’s misled Parliament. 

He added: ‘There is a Privileges Committee set up precisely to look at that...The PM was not prepared to put himself before the committee. Weak and guilty. I couldn’t support the Government line – but I also couldn’t walk through [the voting lobbies] with the Tories.’ 

 He was joined by his fellow MP Jonathan Brash, who last week called for the PM to stand down, who said he would have voted for the motion had he been in Parliament.

He wrote on Facebook: ‘To whip colleagues on a matter of this nature is, in my view, a serious misjudgement and deeply unfair on them.

‘Regardless of the motives of opposition parties, the sensible course would have been for the Prime Minister to refer himself to the Privileges Committee.’

He said that he stood with his colleagues who had voted against, adding: ‘I would have voted for the motion today.’

Bell Ribeiro-Addy, an MP from the left of the party, said on Twitter: ‘I am not in Parliament for today's vote on referring Keir Starmer.

‘If I was, I would be voting for the motion. Transparency is a cornerstone of our democracy.

‘The best thing for the PM to do would be to simply refer himself on this matter and save us all the drama.’

Her fellow Labour MP Navendu Mishra wrote on Facebook that he thought the PM should face the Privileges Committee, but said he couldn’t vote with opposition parties.

‘After careful consideration, I have made the difficult decision to abstain in this vote,’ he said.

‘The Prime Minister maintains that he did not mislead Parliament; as such, a more appropriate response would have been for the Prime Minister to refer himself to the Privileges Committee.’

MPs had been on a three-line whip – which means they risk being booted out of the party and having to sit as independents if they rebel - unless they have an excuse.

They were ordered by whips to vote against the motion for a sleaze probe into whether the PM had lied to Parliament over Lord Mandelson.

Of the 53 abstentions, four were ministers who were away on business or had family matters and four were members of the privileges committee, so were told not to take part.

One MP – Cat Smith – voted both for and against the motion, while another – Cat Eccles – said she would have voted against it had she been in Parliament.

Others said they were ‘slipped’ – so had permission of the whips to not be present – for family matters or for constituency events.

Ian Lavery – an MP on the left of the party – said he was attending a funeral but also tweeted praise for a speech by Emma Lewell, who voted for the motion.

Many others did not respond to requests for comments.

Earlier yesterday, Housing Secretary Steve Reed dismissed the rebels as the 'usual suspects' and played down the prospect of them being booted out of the party.

Asked if they should lose the whip, he told Times Radio: 'There was a handful of usual suspects who did what they tend to do. 

'I’m not in charge of discipline, I’m not too bothered about them to be honest.'

A spokesman for the whips’ office declined to comment on what action would be taken against the MPs who voted against, or abstained.

MPs who voted against the motion included Apsana Begum, Richard Burgon, Ian Byrne, Mary Kelly Foy, Imran Hussain, Brian Leishman, Emma Lewell, Rebecca Long Bailey, Andy McDonald, John McDonnell, Grahame Morris, Luke Myer, Kate Osborne and Nadia Whittome.