The British government suffered a major blow on Wednesday night as Conservative Party rebels allied with Labour and other opposition parties to push through an amendment to Brexit legislation going through the House of Commons.

The amendment will require MPs to have a meaningful say on the terms of Britain’s departure from the EU.

The Conservative rebels were led by Dominic Grieve, Britain’s former attorney general, and came despite a last-minute attempt by the government to offer a “concession” and intense lobbying by party whips, which reportedly included reducing one MP to tears. “It is too late,” Grieve told the House ahead of the vote.

“You cannot treat the House in this fashion.” Anna Soubry, another rebel, highlighted the importance of getting a truly meaningful vote rather than a binary choice that left MPs with little choice but to vote in favour to avoid Britain crashing out of the EU.

“The ability of those of us in this place, acting on behalf of our constituents, to change some of the drift of the negotiations, to get a deal that suits everybody in our country,” she told MPs during the intense debate.

The amendment passed with a margin: 309 MPs supported the motion while 305 opposed it

Brexit supporters The development was met with anger from hardline Brexit supporters.

“Proud of yourselves,” thundered The Daily Mail , which described the 11 Conservative rebels as “self-consumed malcontents” who had betrayed the party and the 17.4-million Brexit voters. The government expressed its disappointment.

“We are as clear as ever that this Bill, and the powers within it, are essential,” a spokesperson insisted.

“This amendment does not prevent us from preparing our statute book for exit day. We will now determine whether further changes are needed to the Bill to ensure it fulfils its vital purpose.”

One of the rebels, Stephen Hammond, was swiftly sacked as the Conservative Party’s vice chair, following the vote.

“This defeat is a humiliating loss of authority for the government of the eve of the European Council meeting,” said Labour Leader Jeremy Corbyn, who accused the prime minister of resisting democratic accountability.

“Her refusal to listen means she will now have to accept Parliament taking back control.”

The defeat was the first major one in Brexit legislation for the government, but may not be its last.

Grieve told the BBC late on Wednesday that he and others would challenge a government-backed amendment to put into law an exit date (11pm GMT on March 29, 2019) from the EU.

The vote came as Prime Minister Theresa May travelled to Brussels for the European Commission’s meeting.

The development casts a shadow over the landmark agreement on the terms of Britain’s exit, after tough negotiations with the EU on the rights of EU citizens, the size of Britain’s divorce payment and the road forward for the Irish border.

Fresh crisis However, just the day after the agreement, May faced another crisis as Brexit secretary David Davis appeared to suggest the agreement wasn’t binding and could be backed down on by Britain: the government has spent the days since attempting to salvage the situation and put on a united front.