EU chief Brexit negotiator Michel Barnier wants any withdrawal deal finalised by October 2018 and the Government has committed to hold a vote in Parliament as soon as possible after the negotiations have concluded.
But Brexit minister Steve Baker told a Lords committee that, if the UK has not reached agreement with the bloc by that time, MPs would not get a vote.
He told this morning’s meeting the UK hoped and expected to get an agreement but would not commit to a Bill or parliamentary motion on leaving in March 2019 if they failed.
Mr Baker warned committee members: “The vote we have committed to is a vote on the withdrawal agreement.
“Both Houses put through the EU (Notification of Withdrawal) Act un-amended and the House of Commons voted for it by a very large majority.
“The terms of that were clearly known to parliamentarians at the time which is that the treaties would cease to apply either when a withdrawal agreement came into force or after two years.
“So the House of Commons in particular has voted by a large majority to exit the EU on that day.
“That is a decision which has been taken.”
Lord Pannick appeared taken aback, asking: “But the constitutional implications of leaving with no agreement would be so enormous.
“Would it not be constitutionally appropriate to seek the approval of Parliament for something like that?”
Mr Baker hit back: “Parliament has approved us exiting the EU on that date, that is my fundamental point.”
He stressed again the Government expected “a good quality deal which works for everyone”.
The exchange came as rebel Tories pushed for a meaningful vote on the terms of the UK’s withdrawal.
Rebel ringleader and former attorney general Dominic Grieve believes he has enough support to defeat the Government this evening unless ministers give in.
Brexiteers have reacted angrily to the threatened revolt, accusing rebels of trying to “derail” the Brexit legislation, which is needed to transpose EU legislation on to the UK statute book when Britain leaves in March 2019.
Mr Grieve, who campaigned for Remain in the referendum, denied his amendment – which would require any final deal with the EU to be approved by a separate act of Parliament before it could be implemented – was designed to prevent Brexit happening.
He said he tabled the change because without it the Government had the power to push the final deal through by the use of statutory instruments.
Mr Grieve said that would deny MPs the vote they have already been promised by ministers on the outcome of the negotiations.
In a bid to a void a Commons defeat, Brexit Secretary David Davis has written to Tory MPs, promising “a number of votes” on the final deal struck between the UK and EU.