Northern Ireland Secretary Brandon Lewis "answered the wrong question" when he said a move to override key parts of the Brexit divorce deal would break international law, a chief government legal officer has said.
The UK Internal Market Bill, which gives ministers the power to overwrite provisions in the withdrawal agreement relating to Northern Ireland, does not "constitute a breach of international law or of the rule of law", Lord Keen of Elie, the Advocate General for Scotland, told peers.
However, the Tory frontbencher's claim led to cries of derision from the opposition benches in the House of Lords.
In unusually strong language for the upper chamber, Lord Keen was accused of having talked "a load of rubbish".
The spat came after Mr Lewis sparked a backlash by admitting that steps being taken by the Government in relation to the withdrawal agreement would break international law in a "specific and limited way".
Lord Keen said: "In my opinion, the present Bill does not of itself constitute a breach of international law or of the rule of law."
But Labour's shadow attorney general Lord Falconer of Thoroton said: "The key characteristic for law officers is not brains - they can get all the advice they want from the English bar of lawyers - it is backbone."
The Northern Ireland Secretary had confirmed the legislation going through Parliament was a breach of international law, while Lord Keen had "produced a load of rubbish" to peers to claim it was not, said the opposition frontbencher.
Lord Falconer asked Lord Keen how he felt he could remain Advocate General.
He replied: "I have satisfied myself as to the correct legal position in this context.
"It is my view that the Secretary of State for Northern Ireland essentially answered the wrong question."
Lord Keen's words sparked groans of dissent. Lord Falconer could be heard to cry in exasperation: "For goodness sake, he is a Cabinet minister."