MPs voted in the House of Commons 461 to 89 in favour of May triggering Article 50 by the end of March 2017, which will begin the formal process of exit negotiations from the 28-member economic bloc.
The win followed a compromise between Opposition Labour and the ruling Conservatives, which saw May committing to revealing the official plan for Brexit before the actual process begins, without committing to any detailed account.
The vote also supported a Labour motion calling for Parliament to “properly scrutinise” the government in its proposals for leaving the EU by 448 votes to 75 – a margin of 373.
Labour’s Brexit spokesman, Sir Keir Starmer, has said his party would continue to challenge the government if its plan was “not detailed enough”.
He said: “I think it’s got to be pretty detailed, they’ve got to set out what those objectives are. I don’t think it needs to be in a particular form, but if it’s not detailed enough they can expect further challenge.”
Brexit Secretary David Davis responded: “The simple fact is that the mandate (in June’s referendum) was to leave the European Union – full stop. We need to keep that in mind when we are going through that process.
“This is a negotiation; it’s not a policy statement. And, therefore, where you are aiming for may not be the exact place you end up.”
The debate today came after a procedural battle between the parties over the wording of the motion to be put to MPs. Mrs May had been refusing to provide a “running commentary” on Brexit after the UK voted to leave the EU in a referendum in June.
As the Supreme Court in London continues to hear a case to establish the extent of British PM’s power in launching into a Brexit without parliamentary approval, Downing Street put forward an amendment agreeing to publish a plan before triggering Article 50 of the Lisbon Treaty.
Starmer described it as “a welcome and hugely significant climbdown”, while the government believes receiving this parliamentary backing for the timetable would avoid delays to the Brexit process.
The government’s amendment was opposed by 23 Labour MPs and one Conservative – former chancellor Ken Clarke. Five Liberal Democrat MPs, three Welsh Plaid Cymru MPs and 51 SNP MPs also voted against it.
(With inputs from agencies)