LONDON (Reuters) - Britain’s government has removed a legislative proposal for a “meaningful vote” in parliament on whatever deal it negotiates to leave the European Union, opposition lawmakers said on Thursday.

The government has proposed amendments to its Brexit legislation after the unelected upper house of parliament made 15 changes to British Prime Minister Theresa May’s original plans, despite ministers’ attempts to block them.

The government decided not to change an amendment that would force it to try to negotiate a customs union with the EU that is shaping up to be the most contentious vote in parliament next week, an official with the opposition Labour Party said.

Labour said that among the amendments was one that removed the requirement for the government to hold a “meaningful vote” in parliament on the deal it will try to negotiate with the EU for Britain’s future relationship with the bloc.

“It is vital parliament has a meaningful vote including in the event of no deal with the EU,” a group of Labour lawmakers in parliament said on Twitter. “Wasn’t Brexit about parliament getting back control?”

No one was immediately available to comment in May’s office.

The government plans to ask lawmakers in the directly-elected lower house of parliament to overturn some of the changes next week.

The debate will test May’s ability to broker a compromise with those in her Conservative Party who, like many members of the upper house, want to keep a relatively close relationship with the EU after Brexit.

Failure to placate those rebels could force a tight vote with serious consequences for both May’s authority as leader of a minority government and the future trading relationship between Britain and the EU.