Sir Keir Starmer will not challenge Donald Trump over his Ukraine comments in Washington next week, one of his key deputies has suggested.

Pat McFadden, the Chancellor of the Duchy of Lancaster, said Sir Keir will “not chase every comment, every statement” in order to maintain good relations with the new US administration.

Speaking at a fringe event at the Scottish Labour conference in Glasgow, Mr McFadden said “we actually can’t conduct policy” by responding to every utterance from Mr Trump and his allies.

Instead he said Sir Keir had to take “a step back from that” and consider what was in the best interests of the British people.

Mr McFadden said that meant “a good and constructive relationship with the United States administration” and leading a revamp of Europe’s defence capabilities. He said the Prime Minister has struck the right tone and balance in recent weeks.

Mr McFadden’s intervention came as Sir Ed Davey, the Liberal Democrat leader, urged the Prime Minister to use his visit to the White House next Thursday to “call out” Donald Trump on Ukraine.