A five-day debate on the Brexit Withdrawal Agreement, which began today at Westminster, will continue tomorrow ahead of a crucial vote on the deal on 11 December.
The debate began after the UK parliament voted that the British government was in contempt of parliament for refusing to release full legal advice on Brexit.
MPs voted 311 to 293 in favour of the motion that found ministers in contempt and ordered the immediate publication of the advice.
Opening the five-day debate late this afternoon, Prime Minister Theresa May said the "only certainty would be uncertainty" if MPs failed to back her Brexit deal.
Mrs May urged the Commons to vote it through, saying: "And don't let anyone here think that there's a better deal to be had by shouting louder.
"Don't imagine that if we vote this down another deal is going to miraculously appear."
"The alternative is uncertainty and risk; the risk Brexit could be stopped, the risk we could crash out with no deal."
She said it would not be in the "national interest" to block the Withdrawal Agreement, adding: "The only certainty would be uncertainty."
Boris Johnson was heckled by fellow Tory MPs as he claimed the EU risks keeping the UK in "permanent captivity" to warn others about trying to leave.
Divisions among the Tory benches were laid bare for all to see in the Commons as the former foreign secretary urged colleagues to reject Mrs May's Brexit deal and claimed Brussels "think they've got us beat".
He also outlined ideas which included renegotiating with the EU and removing the Irish border backstop.
Mr Johnson claimed the UK would be permanently trapped in the Irish border backstop because the EU had "no reason to take its foot off our neck".
He added: "They will keep us in permanent captivity as a memento mori, as a reminder to the world of what happens to all those who try to leave the EU.
"This is a recipe for blackmail and it's open to any member of the EU to name its price for Britain's right to leave the backstop.
"The Spanish will make a play for Gibraltar, the French will go for our fish and our bankers, the Germans may well want some concessions on the free movement of EU nationals and so it goes on."
Earlier, the leader of the Commons Andrea Leadsom told the House of Commons that the government will publish the "final and full" legal advice provided by Attorney General Geoffrey Cox tomorrow.
Labour's shadow Brexit secretary Keir Starmer said that the finding of contempt was "a badge of shame" for the government, with "huge constitutional and political significance".
It is the first time in modern history that a government has been found in contempt of parliament.
Mr Starmer said: "It is highly regrettable that the government has let it come to this, but ministers left the opposition with no option but to bring forward these proceedings.
"By treating parliament with contempt, the government has proved it has lost its majority and the respect of the House.
"The Prime Minister can't keep pushing Parliament away or avoiding responsible scrutiny."
Only hours before the vote, Mrs May had told Cabinet that "candid" legal advice given to ministers must remain confidential, despite a motion passed by the Commons last month demanding the release of the "final and full" papers.
Mr Cox insisted the government has "gone out of its way" to satisfy the call for the release of the legal advice in full.
Speaking in the Commons after the vote, Ms Leadsom said: "We've tested the opinion of the House twice on this very serious subject.
"We've listened carefully and in light of the expressed will of the House we will publish the final and full advice provided by the Attorney General to Cabinet."
Next week's vote on the Brexit deal will be one of the most important - and divisive - votes ever taken in the House of Commons.
The ballot by MPs on whether or not to accept the Brexit agreement reached between Mrs May's government and the EU 27 will take place next Tuesday.
MPs will spend the next five days debating the merits, or otherwise, of the deal.
It will be an uphill struggle for Mrs May to convince an estimated 100 MPs from her own Conservative party, as well as the Democratic Unionist Party which props up her minority government, to support her.
Already thoughts have turned to what the alternatives might be if she is defeated, but Mrs May herself refuses to countenance discussing a 'Plan B'.
Meanwhile, the European Court of Justice's Advocate General has said Britain has the right to withdraw its Brexit notice from the European Union unilaterally.