Lord Keen of Elie QC

The controversial UK Internal Market Bill allows ministers to “disapply” rules agreed over the goods that cross between Britain and Northern Ireland.

Section 45(1) of the bill states that certain provisions “have effect notwithstanding any relevant international or domestic law with which they may be incompatible or inconsistent”.

The resignation comes after Northern Ireland Secretary Brandon Lewis, who told MPs that the bill would break international law in a “specific and limited way”, publicly contradicted Lord Keen, who insisted in the Lords that Mr Lewis was wrong and “the bill does not of itself constitute a breach of international law or of the rule of law”.

Regarded as one of the finest advocates of his generation, Lord Keen’s ferocious court skills gained him the moniker the ‘Rottweiler’ and he was at one time the highest paid member of the Scottish bar, our sister publication Scottish Legal News reports.

In his letter to the Prime Minister, he said: “Over the past week I have found it increasingly difficult to reconcile what I consider to be my obligations as a law officer with your policy intentions with respect to the Internal Markets Bill.

“I have endeavoured to identify a respectable argument for the provisions at clauses 42 to 45 of the bill, but it is now clear that this will not meet your policy intentions.

“In these circumstances I consider that it is my duty to tender my resignation from your government.”