David Cameron has "no intention" of apologising to Donald Trump for calling him "divisive, stupid and wrong", Downing Street has said.
Trump all-but secured the Republican nomination for president on Tuesday after his main rival Ted Cruz dropped out of the race.
Today, George Papadopoulos, a foreign policy adviser to Tump told The Times the prime minister should say sorry for his past criticisms.
However a spokesperson for Cameron said today: "The prime minister has no intention of withdrawing his comments."
In December last year, the prime minister slapped down Trump after the billionaire presidential candidate proposed a ban on Muslims from entering the United States.
It is highly unusual for a British prime minister to publicly attack a US presidential candidate.
Cameron told the Commons in December if Trump visited the United Kingdom the whole country would be united "against him".
Speaking at a press conference in London alongside President Obama last month, Cameron said he did not want to "add to" or "subtract from" his past comments about Trump.
Papadopoulos told The Times: "It’s unfortunate that prime minister Cameron was one of the most outspoken critics of Mr Trump. Not even the Chinese premier came out with negative statements, or other European leaders.
"To see Mr Cameron come out as the most vocal opponent was uncalled for. Considering that we believe that the UK-US relationship should be a cornerstone not just of Nato policy but elsewhere it would be wise for him to reach out in a more positive manner to Mr Trump."
He added: "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."
Other British politicians have also hit out at Trump. Chancellor George Osborne said it was "nonsense" to say, as Trump had, that police "fear for their lives" in London.
"Frankly, Donald Trump’s comments fly in the face of the founding principles of the United States and it’s one of the reasons why those founding principles have proved such an inspiration to so many people over the last couple of hundred years," he said last year.
"I think the best way to defeat nonsense like this is to engage in robust democratic debate and make it clear his views are not welcome."