London CNN  — 

Theresa May suffered the worst day in parliament for a British government in 40 years, losing three crucial votes as lawmakers moved to seize control of the faltering Brexit process.

The Prime Minister’s authority was left hanging by a thread after Members of Parliament found her government in contempt for failing to publish the full legal advice underpinning her Brexit plan.

In a further and potentially more important defeat, lawmakers approved an amendment that aims to give Parliament greater say if May’s Brexit deal is rejected next week. Parliament could then insist on a “softer” Brexit – where the UK would remain in or closely aligned with the EU’s customs union and single market, or even demand a second Brexit referendum.

MPs had already rejected a government compromise on the legal advice, under which the issue would have been kicked to a parliamentary committee. No British government has suffered a worse day at the hands of MPs for 40 years.

May’s minority administration – notionally propped up by the Democratic Unionist Party of Northern Ireland – was left in turmoil as it became clear it could not win support for crucial votes in the House of Commons.

The opposition Labour Party’s Brexit spokesman, Keir Starmer, said the defeat on the legal advice, by 311 votes to 293, was a “badge of shame” for the government. The decision had “huge constitutional and political significance,” he told Britain’s Press Association.

The unprecedented contempt vote was prompted by the government’s refusal to publish the legal advice on May’s Brexit deal, despite having previously accepted a parliamentary motion directing it to do so.

The attorney general, Geoffrey Cox, had argued it was not in Britain’s national interest to publish it in full, and instead offered a summary to Parliament on Monday. “There is nothing to see here,” Cox insisted. May told her Cabinet on Tuesday that “candid” legal advice given to ministers must remain confidential.

Starmer told the House of Commons that the government was “willfully refusing to comply” with the binding order issued by lawmakers. “That is contempt,” he said, adding that the government had ignored the motion for months.

Day of defeats

The day started badly for May’s government when a top EU legal adviser ruled that the UK could unilaterally halt the Brexit process.

In an opinion prepared for the European Court of Justice, the advocate general said the UK did not need the approval of the 27 remaining EU member states to halt the two-year countdown triggered invoking Article 50 of the Lisbon Treaty. The UK government had fought the case, saying it had no intention of stopping the Brexit process.

After the later parliamentary defeats, May opened a five-day Commons debate on her Brexit plans. She urged lawmakers to support her proposals when they come to vote December 11. “This argument has gone on long enough,” May told the House of Commons. “It is corrosive to our politics. And life depends on compromise.”