A LEADING barrister has warned Labour MPs that the pledge on workers’ rights that Prime Minister Theresa May made to persuade them to vote for her Brexit plan is meaningless.

Employment law expert Aidan O’Neill QC issued the legal opinion after a number of back-bench Labour MPs publicly stated that they would support the PM’s deal on the basis of the proposal.

The advice was commissioned by the Independent Workers of Great Britain (IWGB) and TSSA unions. Mr O’Neill told the MPs that the proposal is no guarantee that future EU rights will be matched.

Parliament cannot pass laws that future parliaments cannot change or reverse, so any guarantee would be meaningless, he explained.

IWGB general secretary Jason Moyer-Lee said: “This legal opinion is a damning indictment of the Prime Minister’s non-offer last week.”

TSSA general secretary Manuel Cortes said: “Our rights are hard won and it’s the duty of every Labour MP not to collude with the Tories to get rid of them.”

Ms May failed to make any progress with the EU over the contentious Irish border backstop ahead of a second meaningful vote in the Commons on her Withdrawal Agreement.

Downing Street acknowledged today that negotiations with the EU remain “deadlocked” after a call between Ms May and European Commission president Jean-Claude Juncker yesterday ended with no adjustments to the deal.

In an urgent question today Labour leader Jeremy Corbyn sought to challenge Ms May to explain the state of play of the negotiations, but she was a no-show.

He told the Commons: “The Prime Minister cannot keep dodging scrutiny after failing to get changes to her — overwhelmingly rejected — deal.

“Theresa May must come to Parliament this afternoon and face up to the mess her government has made of the Brexit negotiations.”

Shadow Brexit secretary Sir Keir Starmer insisted it was imperative that the PM respond rather than sending a junior minister.

There was speculation that Ms May could cancel the meaningful vote as she had failed to gain legal assurances that the backstop would not remain indefinitely.

But Tory former minister Nick Boles warned that Ms May’s position would be in jeopardy if she dodged the Commons vote.

In December she postponed the first meaningful vote on the withdrawal deal to the new year, when MPs rejected it by a majority of 230 votes.

Ms May has committed to a vote tomorrow on a no-deal Brexit if her deal is rejected again, and another vote on Thursday — if MPs vote against a no-deal Brexit — on delaying the invocation of Article 50, the legal mechanism for leaving the EU. It is currently set for March 29.