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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.

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 had 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 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.

On Monday, Boris Johnson said if a deal hadn't been done by the time the European Council meets on 15 October, the two sides should "move on" and accept the UK's exit without one.

Shadow Northern Ireland Secretary, Louise Haigh, said it was "deeply concerning" that the prime minister "appeared to be undermining the legal obligations of his own deal" with the introduction of the new law while the negotiations are taking place.