By JILL LAWLESS, AP
LONDON (AP) — Britain's House of Commons voted Wednesday to back Prime Minister Theresa May's March 31 deadline to start the U.K's. formal exit from the European Union, after the government agreed to publish details of its negotiating plan.
The Conservative government has been reluctant to reveal much about its strategy or goals, saying that would weaken its hand in negotiations with the EU.
Fearing defeat through an opposition motion calling for ministers to disclose more details before the talks start, the government agreed to publish a plan. However, it did not make any promises on how specific the plan would be.
The government also proposed a concession of its own by amending the motion to state Parliament's support for triggering EU exit talks by March 31.
The motion passed by a vote of 448 to 75 after the main opposition Labour Party said it would accept the amendment.
Labour Brexit spokesman Keir Starmer said his party was not seeking to block Brexit — backed by a majority of voters in a June referendum — but to bring "clarity, scrutiny and accountability" to the process.
"The terms upon which we leave the EU will define us and our country for many years," he said.
Brexit Secretary David Davis promised the government would set out "strategic plans," but said it would not reveal anything that could "jeopardize our negotiating position."
The vote marked the first major success in efforts by pro-EU lawmakers — including those in Conservative ranks — to influence the course of Brexit. Some 48 percent of electors voted to stay in the bloc, and many want to avoid a "hard Brexit" in which the country leaves the EU single market in goods and services.
Conservative lawmaker Anna Soubry said "remain" voters felt ignored, and implored the government to "include that 48 percent" in plans for leaving the EU.
Both the government and the opposition say the motion is does not affect a case at the Supreme Court over whether the government has the authority to start negotiations without legislation in Parliament. May's government is appealing a lower court's ruling that lawmakers must get a say before Article 50 can be invoked.
Eleven Supreme Court judges are hearing the case, which has major constitutional implications for the balance of power between Britain's legislature branch and the executive.
May plans to trigger Article 50 using ancient powers known as royal prerogative, which enable governments to join or leave international treaties.
Government lawyers argue that Parliament has already had its say, by passing the 2015 law that made June's referendum on EU membership possible.
But David Pannick, one of the lawyers arguing against the government, said Wednesday that the government does not have the power to take Britain out of the EU — removing rights granted to citizens by membership in the bloc — without the approval of lawmakers.
Lawyers from Scotland and Northern Ireland argued Wednesday that their legislatures also must give consent before the government can act, creating another potential obstacle.
The hearing is due to end Thursday, with the judges giving their ruling next month.
The high-profile case has raised the temperature of Britain's debate about how — and whether — to leave the EU.
Police said Wednesday they had arrested a man on suspicion of making online threats against financial entrepreneur Gina Miller, the lead claimant in the lawsuit against the government over Brexit.
The suspect has been released on bail while prosecutors consider whether to charge him. A 38-year-old man from Scotland also has been issued a "cease and desist" notice as part of the same investigation.
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