LONDON (Reuters) - Prime Minister Theresa May defeated the final challenges to her Brexit blueprint in parliament on Wednesday, leaving plans for Britain’s departure from the European Union still largely on track but her authority weakened.

Britain's Prime Minister Theresa May leaves Downing Street for the Houses of Parliament in London, Britain, June 13, 2018. REUTERS/Toby Melville

Lawmakers supported the government’s position to reject amendments to the EU withdrawal bill that challenged May’s commitment to leave the bloc’s customs union and single market, leaving the overall shape of her Brexit strategy intact that will transform Britain’s trading relationships for decades.

But it was a vote in parliament on Tuesday that left her seemingly at the mercy of two groups in the Conservative Party - those who want to maintain the closest possible ties with the EU, and others pressing for a clean break.

An agreement that defused a potential rebellion over handing parliament more control over Britain’s exit from the EU looked in danger of unraveling on Wednesday, when the two camps argued over the shape of a possible compromise on a “meaningful vote”.

Before the vote, she assured lawmakers she would honor her promise and deal with the “concerns raised about the role of parliament in relation to the Brexit process”.

There was little doubt the government would win on the customs union and single market, which some pro-EU lawmakers say is the only way for Britain to retain economically advantageous close ties with the bloc, with the opposition Labour Party also divided over future relations.

Parliament voted 325 to 298 in favor of rejecting a House of Lords amendment to require ministers to report on their efforts in negotiations to secure a customs union.

They also voted against remaining in the European Economic Area (EEA), which offers tariff-free access to the EU’s single market in return for accepting free movement of people, goods, services and capital, by 327 to 126.

LABOUR DISPUTE

Britain’s future trading and customs arrangements after Brexit have become a lightning rod for divisions that have not only plagued May’s Conservative Party but also in the Labour Party.

May had faced the prospect of losing the vote on the customs union after rebels had indicated their support for a change introduced by the House of Lords to require ministers to report what efforts they had made to secure a customs union.

But a government proposal to instead report its efforts to secure a customs “arrangement” was enough to postpone a more searching debate about government policy, with future debates the more likely stage for a revolt.

It won over most of the rebels, but was openly mocked by Ken Clarke, a veteran Conservative who has run at least six government departments, who accused the government of using “pathetic” jargon which was “utterly meaningless”.

In the end, parliament accepted that proposal.

With not all rebels persuaded that May’s plan can prevent an economic shock after Brexit, some say they will challenge her plans to leave the customs union again during votes on other bills, on trade and customs, which will be brought back to the house some time before July 24.

But it was in the Labour Party where the deepest rifts were exposed. Many of its pro-EU lawmakers went against their leader, Jeremy Corbyn, by supporting the vote and not his amendment which argued for a new single market deal with the EU.

Before the vote on the Labour amendment, which the party lost by 322 to 240, lawmaker Laura Smith resigned from her junior role in the team “shadowing” the cabinet office and five others left their roles as parliamentary private secretaries.

Labour’s rebels, many of whom have long criticized Corbyn for his weak support of the EU, were unapologetic.

“This is the moment when we have to tell each other the truth,” said Hilary Benn, a Labour lawmaker who voted for the EEA motion. “There are choices that we face, there are trade- offs that we have to accept.”