The dismissal of Rex Tillerson as US Secretary of State has thrown a sharp spotlight on Donald Trump's failure to voice solidarity with the UK over the nerve gas attack in Salisbury, a senior MP has said.
In one of his final acts as the head of US diplomacy on Monday evening, Mr Tillerson spoke with Foreign Secretary Boris Johnson about the poisoning before issuing a strongly-worded statement expressing "full confidence" in the UK's assessment that Russia was likely to be responsible and calling for the perpetrators to face "appropriately serious consequences".
His comments contrasted with the words of White House press secretary Sarah Huckabee Sanders, who condemned the attack and offered sympathy and support to the UK, but made no reference to possible Russian involvement.
Mike Gapes, former chair of the House of Commons Foreign Affairs Committee, said it appeared Mr Tillerson had been called back to Washington on Monday and may have suspected he was about to be sacked at the time he made his statement.
"It looks as though he used one of his last acts in post to do the right thing and say the right thing about the attempted murders in Salisbury," Mr Gapes told the Press Association.
"One of the last things he did was make a strong statement of solidarity with the UK. And where is Trump's statement?
"Normally it takes Trump five minutes to put something out on Twitter - as he did at the time of the London terror attacks - and yet it is more than a week since Salisbury and he has said nothing."
Mr Gapes described Mr Tillerson's removal as "another example of the dysfunction of Trump's presidency" which had already seen the State Department undermined by the failure to fill key posts.
Labour MP Stephen Doughty, a leading supporter of the Open Britain campaign for close ties with the EU, said the President's "shocking and erratic" behaviour highlighted the risk of relying on support from across the Atlantic.
"Donald Trump simply cannot be seen as a reliable or trustworthy ally of the UK when it comes to standing firm over Russia or any of the other challenges we face, yet the Brextremists want to place the future of our economy in his hands," said Mr Doughty.
"Today's shocking and erratic behaviour by the US President is a reminder of just how big a risk Brexit is for the UK's future."
Labour's former cabinet minister Liam Byrne said: "Secretary Tillerson and the US State Department stood with us over Russia this week - now the White House needs to do the same."