BORIS Johnson was prevented from campaigning in Scotland during the 2014 independence referendum because he was regarded as a “liability” to the pro-Union ground campaign, former members of David Cameron’s Cabinet have suggested.

The claim came as Donald Trump publicly backed the Tory leadership front-runner, telling reporters: “I like Boris Johnson. I spoke to him yesterday. He is going to do a great job.”

Once again criticising Theresa May for doing a “very poor job” on Brexit, which he branded a “disaster,” the US President declared: “Boris will sort it out. He is a different kind of guy. I am a different kind of guy too.”

Mr Johnson, who describes himself as a staunch Unionist, has insisted that he campaigned to keep Scotland in the United Kingdom but three former senior ministers have suggested he did not venture north of border during the whole of the 18-month Yes-No campaign.

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Earlier this month during a visit to Govan, Mr Johnson declared: “What I would say is we had a referendum in 2014, I remember it well, I obviously campaigned on the side of the Union and I believe in it passionately.”

However, one former Cabinet minister, deeply involved in the fight to save the Union, said he did not believe the former London Mayor ever ventured to Scotland during the campaign. “If he had have gone, we’d have known about it because the Nationalists would have been all over him.”

Another told The Herald: “Cameron regarded him as a liability to the ground campaign and stopped him from going to Scotland.”

A third member of the former Prime Minister’s Coalition Cabinet also insisted: “There is a reason why no one remembers Boris going. It’s because he was ordered not to.”

Mr Johnson, who was London Mayor at the time of the independence referendum, did make remarks defending the Union and against Scottish independence during speeches he gave.

In one, at the London School of Economics, in December 2013, he argued Britain would lose its “brand” and be less attractive to incomers if Scotland opted to become an independent nation.

Noting how a Yes vote would result in the epithet the “former United Kingdom” or “F UK,” he asked: “What the F UK do we think we are doing?”

Mr Johnson, who most MPs are now assuming will be elected to replace Theresa May over Jeremy Hunt – the announcement will be made on Tuesday morning at the QEII conference centre opposite the House of Commons - has been a private source of concern for some Scottish Conservatives in relation to the constitutional question for some time.

Last autumn, senior Tories established “Operation Arse” to try to stop the former Foreign Secretary becoming leader. At the time, one of the founders noted: “We called it that, so we’d all be clear who we were talking about.”

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At the time, this prompted Ross Thomson, the MP for Aberdeen South, who is a staunch supporter of Mr Johnson, to brand some of his colleagues “arseholes”.

The depth of concern among some Scottish Tories at the prospect of a Johnson premiership led one MP to warn that if it were ever realised, it would “gift-wrap” independence for Nicola Sturgeon and her SNP colleagues. Another suggested Mr Johnson ensconced in No 10 would “kill off” any chance Ruth Davidson would ever have in becoming First Minister at the 2021 Holyrood election.

Yet, as the leadership contest has unfolded the mood has changed with an increasing number of Scottish Conservative MPs rallying to Mr Johnson’s standard.

A private meeting earlier this week between the leadership frontrunner and the vast majority of his Scottish parliamentary colleagues was described as “positive” and “convivial”. Mr Johnson was said to have reassured them that he would keep the channels open much more than Mrs May ever did and that he would visit Scotland more regularly. His first venture northwards is expected within days of his taking the Conservative crown.

The Herald asked the Johnson campaign for a reply to the claims of his non-appearance during the referendum battle but there was no response.

Meanwhile, Philip Hammond once again refused to rule out voting to bring a new Conservative Government down if there were a no-deal Brexit, saying he would do "everything in my power" to stop such an outcome.

In an interview with European newspapers, the Chancellor said: "I will take steps to avoid an exit without agreement apart from an explicit parliamentary approval.”

He hinted at the possibility of another referendum and asked if he would rule out supporting a motion of no-confidence in the new administration, replied: "I do not exclude anything for the moment."

Tory colleague Stephen Hammond, the UK Health Minister who also rebelled against his Government by abstaining on the Northern Ireland Bill, hinted he would press the "nuclear button" of a no-confidence vote in the new Government were it to pursue a no-deal Brexit.

In other developments -

*Germany’s Angela Merkel raised hopes among Brexiteers after saying the backstop arrangement could be "overwritten" but only if an alternative solution were found, which could be inserted into the declaration on future relationship.

*But the French Government continued to urge Britain to sign up to the draft EU Withdrawal Agreement, firmly rejected by the two leadership candidates.

*An idea touted by some senior Tories to use a parliamentary device known as a humble address to get the Queen involved in stopping a no-deal by going to Brussels to request a Brexit extension was dismissed as "ridiculous" by Lord Sumption, a former UK Supreme Court judge.

*It is suggested some ministers on Wednesday might resign en masse before Mr Johnson has the chance to sack them in a show of defiance.

*Thousands of anti-Brexit campaigners are due to join a "No to Boris, Yes to Europe" demonstration on Saturday from Mayfair's Park Lane to Parliament Square, which will include a “Boris blimp”.