Labour MPs who vote against triggering Article 50 will escape punishment, the party’s Brexit spokesman hinted today.

Keir Starmer said no decision had been taken about the sanction for rebels who defy Jeremy Corbyn – instead promising the conflict would be resolved “collegiately”.

Four Shadow Cabinet members are rumoured to be considering a revolt, although only one – Clive Lewis, the Shadow Business Secretary – has gone public.

Asked what would happen to the “rebels”, Sir Keir said Labour “haven’t made decisions”, adding: “ We are having discussions with colleagues.”

Speaking to Sky News, Sir Keir added: “This is a difficult set of decisions for many colleagues who feel very strongly about these issues

“We are handling it collegiately, talking to people and discussing it in the Labour party in the way you would expect.”

Three frontbenchers were allowed to keep their jobs after rebelling in an earlier vote on triggering Article 50 last month.

And some Labour MPs say they are still pressing for a free vote on the start of EU withdrawal – something Sir Keir appeared to confirm is still under consideration.

Mr Corbyn has said his MPs will only be “asked” to back the start of Brexit – a word falling short of a strict three-line whip.

A failure by Labour to enforce discipline – after Mr Corbyn insisted he would not obstruct Brexit – will be seized on by political opponents.

Further down the line, Labour has tried to paper over the cracks with a vow to seek a “meaningful” vote on the exact form of the UK’s exit from the EU.

Sir Keir suggested the Prime Minister should be forced to go back to Brussels to renegotiate the final deal if MPs and peers vote it down, presumably in 2019.

Mr Corbyn said: “Labour respects the result of the referendum and the will of the British people and will not frustrate the process for invoking Article 50.

“However, Labour will seek to amend the Article 50 Bill to prevent the Conservatives using Brexit to turn Britain into a bargain basement tax haven off the coast of Europe.

“Labour is demanding a plan from the Government to ensure it is accountable to Parliament throughout the negotiations and a meaningful vote to ensure the final deal is given Parliamentary approval.”

Labour will table detailed amendments, including a demand that a “full Brexit plan’ is published before Article 50 is published – something the Government has already rejected.