Britain's House of Commons was opening round two Wednesday in a bruising battle between lawmakers and Prime Minister Theresa May's government over Brexit.

Lawmakers were holding the second of five days of debate on the government's divorce deal with the European Union, before Parliament votes Dec. 11 to accept or reject it.

May is struggling to keep the Brexit deal on track after her government was dealt a double blow by Parliament.

In a historic first, legislators on Tuesday found the government in contempt of Parliament for refusing to publish legal advice it received from the country's top law officer about the agreement.

The government argued that such advice is customarily kept secret. But it bowed to defeat Wednesday and released the reasoning from Attorney General Geoffrey Cox.

The main thrust of Cox's advice was already known — the government released a 43-page document about it Monday in a bid to fend off the contempt motion. But the defeat demonstrated the fragility of May's government, which does not have a majority in Parliament.

The legal advice also has provided fuel to opponents of May's deal, who dislike a "backstop" provision in the agreement that would keep the country in a customs union with the EU to guarantee an open border between EU member Ireland and the U.K.'s Northern Ireland.

The backstop is intended as a temporary measure, but pro-Brexit lawmakers say it could leave Britain tied to the EU indefinitely and unable to strike new trade deals around the world.

The legal advice confirmed that Britain can't unilaterally opt out of the backstop, which requires agreement by both sides. Cox advised that there was a risk the U.K. might become stuck in "protracted and repeating rounds of negotiations."

Politicians on both sides of Britain's EU membership debate oppose the agreement that May struck with the bloc — pro-Brexit ones because it keeps Britain bound closely to the EU, and pro-EU politicians because it erects barriers between the U.K. and its biggest trading partner.

Most signs suggest the government is headed for defeat in next week's vote. That would leave the U.K. facing a messy, economically damaging "no-deal" Brexit on March 29 and could topple the prime minister, her government, or both.

In another blow to May, two dozen Conservative lawmakers voted with the opposition Tuesday to force an amendment to Brexit plans giving lawmakers more say over what happens next if the deal is defeated.

Pro-EU legislators say the amendment makes the prospect of a "no-deal" Brexit less likely, because Parliament can direct the government to take that option off the table.

Brexit-supporting legislators worry that opponents of Brexit in Parliament may try to water down the terms of departure from the EU, or even reverse the decision to leave.

International Trade Secretary Liam Fox said Wednesday that there was "a real danger that the House of Commons, which has a natural 'remain' majority, may attempt to steal Brexit from the British people."

Fox said that would be "a democratic affront" to the 52 percent of voters who opted in a 2016 referendum to leave the bloc.