Former attorney general Geoffrey Cox said the Government “knew” what it was signing up to when it ratified the Withdrawal Agreement.
He told Times Radio: “What I can say from my perspective is we simply cannot approve or endorse a situation in which we go back on our word, given solemnly not only by the British Government and on behalf of the British Crown, but also by Parliament when we ratified this in February, unless there are extreme circumstances which arrive involving a breach of duty of the good faith by the EU.
“In those circumstances, there are then lawful remedies open to us and it is those we should take rather than violating international law and a solemn treaty.”
He continued: “The breaking of the law leads ultimately to very long-term and permanent damage to this country’s reputation and it is also a question of honour to me – we signed up, we knew what we were signing, we simply can’t seek to nullify those ordinary consequences of doing that and I simply can’t support that.
“But, as I’ve said, there may be circumstances in which these powers could be lawfully used and it is those circumstances that the Government needs to define, I believe, to get the support of people like me.
“And, may I say, I find myself in a very sad position – I’m a strong supporter of this Government, I’m a strong supporter of Brexit, but for me the crossing of an important boundary is when the Government says it is going to break the law and a treaty it signed.”