Theresa May has suffered three Brexit defeats in the Commons as she set out to sell her EU deal to sceptical MPs.
Ministers have agreed to publish the government’s full legal advice on the deal after MPs found them in contempt of Parliament for issuing a summary.
And MPs backed calls for the Commons to have a direct say in what happens if her deal is rejected next Tuesday.
Mrs May said MPs had a duty to deliver on the 2016 Brexit vote and the deal on offer was an “honourable compromise”.
Mrs May was addressing the Commons at the start of a five-day debate on her proposed agreement on the terms of the UK’s withdrawal and future relations with the EU.
The agreement has been endorsed by EU leaders but must also be backed by the UK Parliament if it is to come into force. MPs will decide whether to reject or accept it on Tuesday 11 December.
Read: Britain can unilaterally stop Brexit process – EU lawyers
Mrs May said Brexit divisions had become “corrosive” to UK politics and the public believed the issue had “gone on long enough” and must be resolved.
In other Brexit-related developments:
Former UKIP leader Nigel Farage has quit the party in protest at its direction
The BBC said it had been unable to agree a format for a televised Brexit debate between Theresa May and Jeremy Corbyn following discussions with the parties
The pound briefly fell to 18-month lows after the government lost the contempt vote
Former Bank of England Governor Mervyn King likens Brexit deal to appeasement
The UK should be able to unilaterally cancel its withdrawal from the EU, according to a top European law officer
Analysis: A terrible day for May but…
The BBC’s political editor Laura Kuenssberg
Down is up. Up is down. Black is white. And white is black. Friend is foe. Foe is friend. Stop me now, or else I’ll go on forever.
But the point is this – the prime minister has had a terrible day today as the government made history in two excruciating ways.
Ministers were found to be in contempt of Parliament – a very serious telling off – and the government had a hat trick of defeats – the first time since the 1970s that’s happened.
As you’d expect too, MP after MP after MP rose after Theresa May’s remarks to slam her deal as Tory divisions were played out on the green benches, with harsh words exchanged.
But in this topsy-turvy world, the overall outcome of the day for Mrs May’s big test a week tonight might have been not all bad.
What was the legal advice row?
The Commons supported a motion demanding full disclosure of the government’s legal advice, by 311 votes to 293.
The move was backed by six opposition parties, while the Democratic Unionists, which have a parliamentary pact with the Conservatives, also voted against the government.
It came after Attorney General Geoffrey Cox published a summary of the advice on Monday and answered MPs questions for three hours – but said that full publication would not be in the national interest.
Labour had accused ministers of “wilfully refusing to comply” with a binding Commons vote last month demanding they provided the attorney general’s full and final advice.
After Labour demanded the advice should be released ahead of next Tuesday’s key vote on Mrs May’s deal, Commons Speaker John Bercow said it was “unimaginable” this would not happen.
In response, Commons Leader Andrea Leadsom said she “would respond” on Wednesday but would ask the Commons Privileges Committee to consider the constitutional repercussions.
An attempt by ministers to refer the whole issue, including the government’s conduct, to the committee of MPs was earlier defeated by four votes.
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The privileges committee will now decide which ministers should be held accountable and what sanction to apply, with options ranging from a reprimand to the more unlikely scenario of a minister being suspended from the Commons.
Lib Dem leader Sir Vince Cable said the result left the government “on the ropes”, adding: “Theresa May’s majority has evaporated, and the credibility of her deal is evaporating with it.”
MPs seek to influence Brexit process
The prime minister suffered a further setback on Tuesday as MPs backed, by 321 votes to 299, changes to the parliamentary process should the Commons vote down her deal next week.
If that happens, the government has 21 days in which to return to the House and set out what it plans to do next.
But Tory Dominic Grieve’s motion means that instead of MPs being confined to merely taking note of what the government tells them, the Commons would be able to exert more influence by voting on what they wanted the government to do as well.
Tuesday’s vote, in which 26 Tory MPs rebelled, could potentially tilt the balance of power between government and Parliament if, as expected, MPs push for a “Plan B” alternative to Mrs May’s deal and also seek to prevent any chance of a no-deal exit.
Mr Grieve, who has expressed support for another Brexit referendum, told Channel 4 News he was not seeking to “guarantee a particular outcome” if Mrs May’s deal went down.
But he said it would “allow the UK time to consider its options” – including potentially re-starting negotiations with the EU or giving the public the final say.