A government minister has said a new bill to amend the UK’s Brexit deal with the EU will “break international law”.
Concerns had been raised about legislation being brought forward which could change parts of the withdrawal agreement, negotiated last year.
Northern Ireland Secretary Brandon Lewis conceded it would go against the treaty in a “specific and limited way”.
Former PM Theresa May warned the change could damage “trust” in the UK over future trade deals with other states.
The permanent secretary to the Government Legal Department, Sir Jonathan Jones, has announced he resigning from government in light of the bill, making him the sixth senior civil servant to leave Whitehall this year.
Sir Jonathan, who is the government’s most senior lawyer, is understood to have believed the plans went too far in breaching the government’s obligations under international law.
Labour leader Sir Keir Starmer condemned the bill and accused No 10 of “reopening old arguments that had been settled”, saying the “focus should be on getting a [trade] deal done” with the EU.
No 10 revealed on Monday that it would be introducing a new UK Internal Market Bill that could affect post-Brexit customs and trade rules in Northern Ireland.
Downing Street said it would only make “minor clarifications in extremely specific areas” – but it worried some in Brussels and Westminster that it could see the government try to change the withdrawal agreement, which became international law when the UK left the EU in January.
The row also comes at the start of the eighth round of post-Brexit trade deal talks between the UK and the EU.
The two sides are trying to secure a deal before the end of the transition period on 31 December, which will see the UK going onto World Trade Organisation rules if no agreement is reached.