(CNN) The frosty British reaction to Republican frontrunner Donald Trump continued Wednesday, with the UK's Prime Minister branding Trump's proposed Muslim travel ban "stupid," and the former leader of Scotland labeling the mogul "three times a loser."

Prime Minister David Cameron was responding to a question from an opposition lawmaker on whether he would use anti-extremism legislation to block Trump from visiting the UK, in line with growing calls to do so following Trump's proposal to ban Muslims from entering the United States.

Cameron said Trump's proposal was "divisive, stupid and wrong," but that he did not support a British ban on the U.S. presidential hopeful entering the country.

"If he came to visit our country, I think he would unite us all against him," he told British parliamentarians.

A British petition calling for the U.S. presidential hopeful to be banned from entering the UK has attracted more than half a million signatures since it was launched last week -- more than five times the amount required for a committee to consider sending the motion for parliamentary debate.

Trump loses court case

Meanwhile, Trump became embroiled in a war of words Wednesday with Alex Salmond, a British lawmaker who was the previous First Minister of Scotland.

The spat flared after Britain's Supreme Court unanimously knocked back Trump's appeal against a wind farm being built overlooking one of his high-end golf courses in Scotland -- a case which pitted the businessman-turned-politician against the Scottish government, which had approved the development.

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Trump, whose mother was Scottish, has spent years fighting the installation of 11 offshore turbines within sight of his Trump International Golf Links in Aberdeen, Scotland, arguing they would be a blight on the coastal landscape.

"It's once, twice, three times a loser for Mr. Trump," Salmond told CNN, referring to his case's progress through successive courts of law.

He told CNN the Scottish government had originally welcomed Trump's golf business plans, but found that they did not deliver promised economic benefits to the region.

He argued that Trump had alienated Scottish people in his business activities in the country, and that could affect his electoral prospects in the United States.

"If Donald Trump turns off people in Scotland, then he's likely to turn off Scots-Americans as well," he told CNN.

"It looks like Scots-Americans are going to be added to this ever-growing list of people alienated by Donald Trump."

Trump: Salmond a 'has-been'

The Trump Organization shot back in a statement from executive George Sorial, saying the outcome "demonstrates the foolish, small minded and parochial mentality which dominates the current Scottish Government's dangerous experiment with wind energy."

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In a second statement from the Trump Organization, a representative labeled Salmond, who was the leader of Scotland's parliament until last last year, as "a has-been and totally irrelevant."

"Does anyone care what this man thinks?" read the statement.

"He should go back to doing what he does best -- unveiling pompous portraits of himself that pander to his already overinflated ego."

The Trump Organization threatened to appeal to European courts against the verdict.

Trump loses honorary degree

Trump's rise to prominence as the frontrunner in the Republican presidential race has provoked an uncharacteristically strong reaction from public figures and institutions in the UK, where his Muslim ban proposal and issues around his golf resort have rankled.

The presidential contender's remarks, in the wake of the San Bernardino terror attacks, that parts of London were so radicalized that British police feared for their lives, drew condemnation from a range of leaders.

Cameron, who doesn't usually comment on U.S. presidential candidates, described the comments as "divisive, unhelpful and quite simply wrong," while London Mayor Boris Johnson labeled them "complete and utter nonsense," adding that "the only reason I wouldn't go to some parts of New York is the real risk of meeting Donald Trump."

The Scottish creator of the petition to ban Trump, Aberdeen resident Suzanne Kelly, had earlier launched a petition calling on her city's Robert Gordon University to strip the businessman-turned-politician of an honorary degree it bestowed on him five years ago.

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Last Wednesday, the university announced that it had done so, owing to Trump having made "a number of statements that are wholly incompatible with the ethos and values of the university" during the presidential campaign.

"The university has therefore decided to revoke its award of the honorary degree," said a spokesman for the university.

Kelly had previously campaigned against Trump's political and business activities, documenting issues with Trump's development of the Aberdeen golf course. The project brought Trump into conflict with locals since he bought the estate on protected coastal dunes in 2006 and began developing it into a golf resort.