Britain's parliament and not Prime Minister Theresa May's government will now have the final say on the UK's divorce from the European Union.
British Prime Minister Theresa May on Wednesday suffered a damaging parliamentary defeat over Brexit, after her own MPs rebelled to demand parliament have the final say on the divorce deal with Brussels.
Members of May's Conservative party joined with opposition lawmakers to inflict the government's first defeat over the flagship EU (Withdrawal) Bill, sparking huge cheers in the House of Commons.
Ministers had sought to buy off the rebels with a last-minute promise of a parliamentary vote on the separation agreement, but their leader, former attorney general Dominic Grieve, warned: "It's too late."
His amendment demanding a statutory vote on the deal before Britain leaves the EU in March 2019 passed by 309 votes to 305.
The Brexit ministry said it was "disappointed".
"We will now determine whether further changes are needed to the bill to ensure it fulfils its vital purpose," the ministry said in a statement.
TRT World's Simon McGregor-Wood explains the significance of the vote.
Blow to May
It is a blow to May on the eve of a crucial summit in Brussels, where EU leaders are expected to approve the terms of the interim Brexit deal agreed last week after months of tortuous negotiations.
Gina Miller, a leading pro-EU campaigner, reacted saying: "Parliamentary sovereignty wins the day!"
But Nigel Farage, a key driving force behind the Brexit campaign, said: "My contempt for career politicians knows no bounds".
The EU (Withdrawal) Bill is intended to formally end Britain's membership of the EU, as well as smooth its exit by transferring thousands of pieces of European legislation onto the UK statute books.
It also gives ministers powers to amend the laws as they move across, to address any technical glitches.
But MPs objected to the fact that these so-called "Henry VIII" powers also extend to the implementation of the withdrawal agreement with the EU.
Tory MP Iain Duncan Smith, a hardline Brexiteer, had accused Grieve of "looking for ways to derail the bill", saying his amendment would "tie the government's hands" in negotiations with the EU.
But one Conservative MP, Antoinette Sandbach, had warned: "The government is presiding over a monumental task of immense importance for the future of this country.
"With any such change it is imperative that parliament maintains close scrutiny and oversight of the process."
In a written statement to parliament earlier Wednesday, Brexit Secretary David Davis promised that no withdrawal agreement would be implemented until a vote in both Houses of Parliament.
Parliament would then be asked to approve a further piece of legislation to implement the deal.
But ministers wanted to preserve their special powers in the event that this law is not passed in time.
"That could be at a very late stage in the proceedings, which could mean that we are not able to have the orderly and smooth exit from the European Union that we wish to have," May told MPs earlier.
After months of wrangling, May secured a deal last week on three priorities of the separation – Britain's financial settlement, the Irish border and the rights of expatriates.
It was a rare moment of triumph for the prime minister, who has been struggling to assert her authority since losing her parliamentary majority in a disastrous election in June.
The European Parliament on Wednesday gave its backing to the deal, and EU leaders meeting in Brussels on Thursday and Friday are expected to give the green light to move the Brexit negotiations onto trade.
However, the sense of victory has been tempered by a dispute with Brussels over comments made by Davis at the weekend, suggesting Britain was not fully committed to the agreement.
Wednesday's vote spells further domestic trouble ahead for May, as parliament and her party are divided about Britain's future relationship with the EU.
Ahead of Wednesday's vote, Grieve warned that ministers were asking for "a blank cheque to the government to achieve something that, at the moment, we don't know what it is".