Prime Minister Theresa May’s government on Wednesday suffered its 15th defeat on legislation that will end Britain’s membership of the European Union when parliament’s upper chamber voted in favour of adding environmental safeguards to the bill.

May has to get the bill approved by both chambers of parliament well in advance of Britain’s exit on March 29, 2019, but the House of Lords, the unelected upper house, has demanded major changes that will force a showdown over coming weeks.

The Lords voted 294 to 244 in favour of a change to the bill which would force the government to maintain the EU’s environmental principles. The government argues that Brexit will allow Britain to improve environmental protections through separate legislation.

May’s Conservative government has already suffered high-profile defeats on core Brexit issues.

Martin Callanan, a junior Brexit minister who is a member of the House of Lords, said the government had listened to constructive suggestions to improve the legislation which is now due to return to the lower house.

“However, during the bill’s journey through the House of Lords some changes have been made that conflict with its purpose or are designed to frustrate the entire exit process and so we are considering the implications of those decisions,” he said.

While the more powerful House of Commons can overturn the changes, they may embolden rebels in May’s own party who favour a softer EU exit.

Ministers have accused the House of Lords, where the Conservatives do not have a majority, of making unnecessary changes and have indicated they will fight some of them back in the Commons.

That process, known as ‘ping pong’, is not yet scheduled, but will be a key test of May’s ability to govern effectively and to deliver on her Brexit plans with just a slim working majority in the Commons, where she relies on the support of a small Northern Irish party.

U.K. to tell EU it is ready to stay in customs union beyond 2021: report

Britain will tell Brussels it is prepared to stay in the EU’s customs union beyond 2021 as ministers remained deadlocked over a future deal with the bloc, the Telegraph newspaper reported on Wednesday.

May’s top ministers involved in the Brexit strategy agreed this week on a new last-resort plan to avoid a hard Irish border, having rejected earlier proposals from the EU, the newspaper said.

May has said Britain will leave the EU’s customs union allowing the country to forge its own trade deals around the world.

But her cabinet is split over what kind of future customs system London should seek with the bloc.

Ministers meeting on Tuesday agreed that Britain should try to stay aligned with the customs union if technology needed to operate borders under one of the government’s proposals is not ready in time for 2021, the Telegraph said.

Officials have warned it may not be in place until 2023, the newspaper said.

EU chief negotiator Michel Barnier said on Monday no significant progress had been made in the Brexit talks since March. May wants to clarify her plans before an EU leaders’ summit in June and to seal a deal on Britain’s new relationship with the EU in October, less than six months before Brexit.

A spokeswoman for May declined to comment on the Telegraph report.

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