British politicians vote in favour of giving parliament the final say on any withdrawal deal with the European Union.

British politicians have voted to give parliament the final say on any withdrawal deal with the European Union, dealing a blow to Prime Minister Theresa May on the eve of a crucial summit in Brussels.

MPs on Wednesday voted for an amendment to demand parliament pass a separate bill to approve any final agreement signed with the bloc.

May lost by a narrow margin of 309 to 305 votes. The UK is scheduled to leave the EU on March 29, 2019.

The prime minister had promised legislators a “meaningful vote” on the UK’s deal for its departure from the EU, or Brexit.

Rivals, however, said that the pledge did not go far enough.

‘Doesn’t stop Brexit’

Nina Schick, an expert on European politics, said the outcome of the vote was “expected”, as several members of parliament from May’s Conservative party, which lacks an overall majority, had earlier declared that they would vote against the government.

“What the Conservative rebels wanted is to have enshrined in the EU Withdrawal Bill, which is the active legislation whereby all of the EU law is going to be transposed into UK law, a commitment that there will be a separate bill in which to enshrine the withdrawal process,” she told Al Jazeera.

Schick noted that the vote in parliament “doesn’t actually stop Brexit”.

“This is a very symbolic protest by Conservative MPs who don’t believe in the government’s current course on Brexit.

“What they’re trying to do by defeating the government is … to show that the power of parliament is sovereign over the government.”

A spokesperson said the government was “disappointed” by the vote, adding that “this amendment does not prevent us from preparing our statute book for exit day”.

The defeat, however, comes at a difficult time for May.

On Thursday, the prime minister will attend a two-day EU summit where leaders are expected to approve the terms of a preliminary Brexit deal, which were agreed to last week after months of painstaking negotiations, before moving to the second phase of the talks.

May has been under pressure ever since holding a snap election in June, which resulted in the Conservatives losing their governing majority and negotiating a deal with Northern Ireland’s Democratic Unionist Party (DUP).

The Conservatives rely on the DUP, which has 10 seats in parliament, to pass legislation.