ALEX Salmond has urged Scots-Americans to reject "the nightmare" of Donald Trump winning the US presidency and getting his finger on the nuclear button as the billionaire businessman became the presumptive republican nominee after his last rival, Ohio Governor John Kasich, pulled out of the race.

During his weekly radio phone-in, the former Scottish First Minister said that one of the few things that made him lose sleep was the prospect of “the Donald” - who clashed with him over Scotland's renewable energy policy and its impact on Trump golf courses in Scotland - entering the White House.

Mr Salmond also suggested while there were “Teflon candidates” such as Bill Clinton and “perhaps myself”, Mr Trump's main Democrat rival Hilary Clinton was the “Velcro candidate”, who, after many years in politics, was "vulnerable" to public criticism as smears stuck to her.

Asked about Mr Trump’s latest primary win in his bid for the republican presidential nomination, the MP for Gordon declared: “The nightmare gets worse and worse." He urged US voters to elect "ABD; anybody but Donald".

He went on: "Let's consider the awful prospect that Donald might actually get his finger on the nuclear button and his bottom on the seat in the Oval Office. Hopefully, America will redeem its reputation and, in particular, my appeal to Scots-Americans is: just remember that man would let down America just as he has let down Scotland.”

Mr Salmond admitted there were “few things in politics and life that make me lose sleep but Donald in the White House would be one of them".

Meantime, No 10 made clear David Cameron had "no intention" of withdrawing his condemnation of comments by Mr Trump as "divisive, stupid and wrong".

George Papadopoulos, an adviser to the billionaire businessman, called on the Prime Minister to apologise to the tycoon after the withdrawal of his main rival Ted Cruz made him all but certain of securing the Republican nomination.

The Prime Minister could face difficulties after he criticised Mr Trump last December during a Commons debate on whether or not to ban him from the UK over his call for a "total and complete shutdown of Muslims entering the United States".

The PM told MPs he opposed a travel ban on the republican candidate but added: "His remarks are divisive, stupid and wrong. If he came to visit our country, he would unite us all against him."

Mr Papadopoulos claimed Mr Cameron's comments were "uncalled-for" and it would be "wise" for him to "reach out in a more positive manner" to the Republican front-runner.

He added: “It would seem that if Prime Minister Cameron is serious about reaching out, not only to Mr Trump's advisers but to the man himself, an apology or some sort of retraction should happen.”

The PM’s spokeswoman replied: "The PM has no intention of withdrawing his comments, which were made in response to comments that Donald Trump made calling for a ban on Muslims entering the US. That was the context for the PM's comments."

Mr Trump won the Indiana primary, which led to his main rival Ted Cruz pulling out of the race on Tuesday; 24 hours later his other rival Mr Kasich followed suit.

Blocking from winning the nomination outright, Mr Cruz and Kasich had hoped to force a so-called “contested convention”, when party officials, not voters, would choose for the republican party’s nominee.

However, it now seems all but certain that Mr Trump will have the 1,237 delegates needed to become the nominee before the July convention in Cleveland, Ohio.