DONALD Trump has been branded a “serial child-abuser” over the US administration’s treatment of child migrants as Scottish MPs pressured the UK Government to cancel next month’s presidential visit to Britain.

During Foreign Office Questions in the Commons, Boris Johnson insisted the US President’s visit on July 13 was “absolutely vital” to UK-US relations and suggested that it was the intervention of Theresa May, which had prompted Mr Trump to reverse his Government’s policy of separating child migrants from their parents.

But the Foreign Secretary faced a barrage of questions and expressions of opinion from Scottish MPs, the most stark of which came from the SNP’s Peter Grant, who said it was now time for Britain to question whether the US President was a “fit and proper person” to be the UK’s chief ally.

The MP for Glenrothes told MPs: “This is somebody who can only be described as a serial child-abuser. Putting children into concentration camps is not acceptable. He has not yet taken them out of these camps, he is holding them hostage to force the parents to give up their claims to asylum. He is also trying to abolish due process by having no courts and no judges to decide on them.

“How can this person be fit for a state visit?”

Mr Johnson replied: “The President of the US has repealed the policy in question. He remains the head of state of our most important economic, military and security ally.”

Labour’s Paul Sweeney suggested the Prime Minister’s response to the US’s policy of “ripping toddlers from their mothers and holding them in cages” was merely to say it was wrong and he urged the Foreign Secretary to go further and reflect the British public’s “genuine outrage at this obscene policy”.

Mr Johnson insisted Mrs May’s remarks spoke for the nation, noting: “No sooner had she spoken than he would have noticed the President signed an executive order repealing the policy.”

The SNP’s Chris Stephens, pointing out how human rights campaigners had suggested the American Government’s policy was tantamount to torture, also questioned whether it was appropriate for Mr Trump to visit the UK in such circumstances.

The Secretary of State stressed again that the President had repealed the policy and it was “still common ground” across Parliament to welcome the US's head of state.

But Drew Hendry, the Nationalist MP for Inverness, Nairn, Badenoch and Strathspey, kept up the pressure.

Noting how Mr Johnson was a “self-confessed admirer” of Mr Trump, the backbencher also pressed him to condemn the policy of taking children away from their parents and putting them in cages. “The language we have heard so far does not condemn this action,” he declared.

The Foreign Secretary insisted the PM had indeed condemned it. “No sooner had she spoken than the President of the US repealed the policy, thus demonstrating, I venture to suggest, the considerable and growing influence of the UK.”

But Neil Gray, the SNP MP for Airdrie and Shotts, noting how children were still being kept in cages, asked: “How can he sit there and agree this visit should still go ahead?”

Mr Johnson responded by saying that Mr Trump was the head of state of Britain’s most important ally and it was “common ground among many people of this country that we should extend the hand of friendship to the office of the President of the US”.

He later insisted he and the PM spoke “with vigour” to Washington when the UK Government disagreed with US policy and he added: “The PM and I disagree with what he has been doing with the separation of kids from their parents. It’s right for the UK to speak out on that and we will.”

During question-time Labour’s Emily Thornberry also launched an attack on Mr Trump and his planned visit to the UK in two weeks’ time, asking Mr Johnson: “Surely he knows in the depths of his soul that when we have a President like Donald Trump, who bans Muslims and supports Nazis, who stokes conflict and fuels climate change, who abuses women and cages children, that is not a record to be admired, that is a record to be abhorred.

“I simply ask the Foreign Secretary not just why he joked that a man like that should be in charge of our Brexit negotiations but why he thinks, seriously, that a man like that should have the honour in two weeks’ time of visiting Chequers, Blenheim Palace and Windsor Castle and shaking hands with Her Majesty the Queen?”

The Foreign Secretary said he had already explained where the UK’s views coincided and differed with the US. “But the fundamental point on which I and she are in complete agreement is that it is right that the UK should welcome to this country the head of state of our most important and most trusted ally," he declared.

“She is on record of saying that in the past. If she now dissents from that view, that would be surprising and I would be interested to hear it from her own lips,” added Mr Johnson.

Ms Thornberry wanted to return to the dispatch box to answer the question but the Speaker pointed out how she had already had her mandatory two questions.

At the weekend, the Shadow Foreign Secretary indicated she would be happy to meet Mr Trump, despite describing him as an "asteroid of awfulness," telling BBC One's Andrew Marr Show: "If we get an invitation to see him, of course we will go and see him."