LONDON (Reuters) - Prime Minister Theresa May’s government was found in contempt of parliament on Tuesday for refusing to release its full legal advice on Brexit, underlining the depth of opposition among MPs to her deal on leaving the European Union.

Britain's Prime Minister Theresa May leaves 10 Downing Street in London, Britain, December 3, 2018. REUTERS/Henry Nicholls

The row threatened to overshadow the start of five days of debate in parliament on May’s Brexit deal ahead of a crucial vote on Dec. 11, when MPs will be asked to approve it.

Opposition parties and the small Northern Irish party that props up May’s minority government are furious that it only provided an outline of the legal basis for its Brexit deal after parliament voted to be given the full advice.

They put forward a motion, which was backed by 311-293 in a vote on Tuesday, that found ministers in contempt of parliament and ordered the immediate publication of the advice.

“Today’s finding of contempt is a badge of shame for this government. It is of huge constitutional and political significance,” Keir Starmer, the opposition Labour Party’s Brexit spokesman, said after the vote. “Never before has the House of Commons found ministers in contempt of parliament.”

The sanctions ultimately available include suspending a lawmaker, most likely Attorney General Geoffrey Cox. It was not clear whether the opposition parties would now push for that.

Such punishment is usually reserved for backbench MPs guilty of individual wrongdoing. In reality, Tuesday’s vote was about putting pressure on a weakened government.

Catherine Haddon, senior fellow at the Institute for Government, said the opposition wanted to use “every opportunity they have to show the instability of the government”.

The small Northern Irish party, the Democratic Unionists, which props up May’s minority government, joined opposition parties in voting against the government on the contempt issue.

So many MPs - from May’s own Conservatives as well as from the opposition parties - have spoken out against the deal that the odds look stacked against her winning the Dec. 11 vote.

Haddon said the contempt motion was a “show of force” which could foreshadow both the final vote on the deal and the various amendments MPs are trying to attach to it.

Cox gave parliament an outline of his legal advice to the government on Monday.

Andrea Leadsom, Leader of the House of Commons, said on Tuesday that this had been a “full and frank exposition”, and that releasing the full advice would set a dangerous precedent.

She said the government, which had sought to slow down the process by referring the issue to parliament’s Committee of Privileges, had fulfilled the spirit of the order to publish.

The government said after the vote that it would now publish the full advice.