The House of Lords has voted to give parliament a veto over the final outcome of Theresa May’s Brexit negotiations, inflicting a second defeat on the government’s article 50 bill.

Peers supported a Labour-led amendment by 366 to 268, despite the government’s argument that it would “damage the national interest” by making May’s Brexit negotiations more difficult.

Michael Heseltine, the Conservative former deputy prime minister, was one of those leading the rebellion against the government’s position, along with Labour, Liberal Democrat and crossbench peers.

“Everyone in this house knows that we now face the most momentous peacetime decision of our time,” he said. “And this amendment secures in law the government’s commitment ... to ensure that parliament is the ultimate custodian of our national sovereignty.

“It ensures that parliament has the critical role in determining the future that we will bequeath to generations of young people.”

The government had rejected the amendment, saying it would weaken May’s hand by denying her the ability to walk away from the negotiating table.



George Bridges, a Tory peer and minister, said it would “make negotiations much harder from day one for the prime minister” by increasing the incentive for EU countries to offer the UK a bad deal in the hope of getting parliament to scupper Brexit.

The Brexit bill will now return to the House of Commons with the amendment forcing May to have a vote on her Brexit deal and another guaranteeing the rights of EU citizens.

MPs are likely to overturn those amendments, although some Conservative MPs remain unhappy that it is not clear whether parliament will get a vote if May ends up trying to take the UK out of the EU without a deal having been struck.

This will send the Brexit bill back to the House of Lords, which may end up backing down and acknowledging the supremacy of the Commons.

May has already verbally promised that parliament will get a vote on her Brexit deal but this will be on a “take-it-or-leave-it” basis, as the choices would be accepting the terms or crashing out of the EU to rely on World Trade Organisation rules.

But the House of Lords decided that the promise of a parliamentary vote on the outcome of the Brexit talks with the EU must be set down in legislation. Earlier, the peers voted against putting the outcome to a second referendum.

There were heated clashes in the Lords as a string of Conservative peers accused other members of trying to frustrate the progress of Breixt.

Lord Forsyth, the former Scotland secretary, said: “These amendments are trying to tie down the prime minister. Tie her down by her hair, by her arms, by her legs, in every conceivable way in order to prevent her getting an agreement, and in order to prevent us leaving the European Union.”

Nigel Lawson, a former Conservative chancellor, said the amendment forcing a parliamentary vote regardless of the outcome of talks would be an “unconscionable rejection of the referendum result, which would drive a far greater wedge between the political class and the British people than the dangerous gulf that already exists”.

The only practical effect would be to create a “political crisis” with highly damaging uncertainty for business and the economy which could only be resolved by a general election, he said.

But another former Tory cabinet minister, Douglas Hogg, denied supporters of the move wanted to stand in the way of the bill.

“The sole purpose is to ensure the outcome – agreed terms or no agreed terms – is subject to the unfettered discretion of parliament,” he said. “It is parliament, not the executive, which should be the final arbiter of our country’s future.”

The amendment would not only enable parliament to reject a “bad deal” but to “prevent Brexit altogether by refusing to allow the UK to leave the EU without agreement”, he added.