Sir Keir Starmer has said Labour will seek to call a motion of no confidence in the Government if Theresa May loses a Commons vote on her Brexit deal.
The shadow Brexit secretary told Sky News' Sophy Ridge on Sunday: "It seems to me that if the Prime Minister has lost a vote of that sort of significance then there has to be a question of confidence in the Government...
"I think it's inevitable that we will seek to move that - obviously it will depend on what actually happens in nine days, it will depend on what the response is - but if she's lost a vote of this significance after two years of negotiation, then it is right that there should be a general election.
"Because, but for the Fixed Term Parliaments Act, the convention was always if a Government loses what's called a confidence vote - something of such significance - then that Government has to go."
Conservative Brexiteer and former Cabinet minister Theresa Villiers also said she would "have to look at the circumstances" before deciding how to vote if a no confidence motion in the Prime Minister was called.
She told Sky News' Sophy Ridge on Sunday: "I would certainly vote against any motion of no confidence in the Government.
"If there was a confidence resolution in relation to the Prime Minister, I would have to look at the circumstances at the time, but my present intention would be to vote to have confidence in the Prime Minister."
At the end of the G20 summit Theresa May said she will be the Prime Minister to take the UK out of the European Union.
She indicated she does not believe her premiership will end with Brexit, insisting "there's a lot more for me still to do".
She said that world leaders had expressed their desire for "certainty" about the UK's future position.
Mrs May is due to arrive back in the UK later today.
