Jacob Rees-Mogg has said Article 50 and European Union law supersedes the Benn Act, which is designed to prevent a no-deal Brexit.
Speaking on the fringe of the Conservative Party conference in Manchester, the Leader of the House of Commons said the situation was “very straightforward”.
“You may remember how we got the extension from March 29. We did not get it by an Act of the UK Parliament, we got it because as long as the 1972 European Communities Act is enforced, EU law is more powerful than UK law,” he said.
“So Article 50 and EU law overrides the Benn Act, and if [Brexit opponent] Dominic Grieve were here he'd say the same thing.”
The Benn Act orders the Prime Minister to ask the EU for an extension of the October 31 Brexit deadline if no deal is reached by October 19.
Boris Johnson has said he would not ask for an extension, but has also confirmed to talkRADIO he would respect the law.
Mr Rees-Mogg admitted there was “no easy and obvious loophole” that would allow the Prime Minister to circumvent the Act.
Some have suggested Mr Johnson could send a letter to the EU asking for an extension, and then send a second letter which made it clear he did not wish his request to be taken seriously.
However, such a move could trigger a constitutional crisis and would likely be resolved in the courts.
The Prime Minister will address the conference on Wednesday and said he will table his withdrawal proposals to the EU “very soon”.