Justice Secretary Robert Buckland has said he would be prepared to resign if the UK ended up “unacceptably” breaking international law over Brexit.
He said he was committed to upholding the rule of law and defended plans to potentially override the EU Withdrawal Agreement as an “insurance policy”.
Asked if he would quit if negotiations with the EU on other solutions failed, he said “we are not at that stage”.
The proposed law, the Internal Markets Bill, will be debated by MPs on Monday.
Labour have indicated they will not support it unless big changes are made.
Pressure is mounting on those Conservative MPs who are sceptical about the legislation to vote oppose it in the Commons, with former prime ministers Tony Blair and Sir John Major calling it “shaming and embarrassing”.
And Irish foreign affairs minister Simon Coveney said it was “completely bogus” for the UK to claim that the EU was interpreting the Withdrawal Agreement in a way which could led to the break-up of the UK.
Boris Johnson has said the European Union is threatening to impose a customs border in the Irish Sea, separating Northern Ireland from the rest of the UK.
If the Internal Markets Bill becomes law, it will give UK ministers powers to modify or “disapply” rules relating to the movement of goods between Britain and Northern Ireland that will come into force from 1 January, if the UK and EU are unable to strike a trade deal.
Appearing on the BBC’s Andrew Marr, Mr Buckland said the bill was a “break the glass in an emergency” safeguard which he hoped would never be used, as a solution could be found through the existing negotiating process.
The Lord Chancellor acknowledged there was a “dichotomy” between the UK’s positions in domestic and international law but indicated he was comfortable with this at the moment as steps were being taken to resolve it.
Pressed on whether he would quit if the UK did end up breaking international law, he replied: “If I see the rule of law being broken in a way which I find unacceptable, then of course I will go. We are not at that stage.”
He added: “I don’t believe we will get to that stage. I know in my mind what we have to do.
“The government collectively also has a responsibility. We have to resolve any conflict and that is what we will do.”