A letter from Donald Trump's New York physician released by his campaign in 2015 declaring he would be, "the healthiest individual ever elected to the presidency" was composed by the candidate himself, the doctor has said.

"He dictated that whole letter. I didn't write that letter," Harold Bornstein told CNN.

Dr Bornstein was not immediately available to comment, but in a subsequent interview with NBC News he confirmed the account.

The White House did not immediately respond to a request for comment.

"Mr Trump has had a recent complete medical examination that showed only positive results," said the letter signed by Dr Bornstein, who said he had treated Mr Trump since 1980.

"Actually, his blood pressure, 110/65, and laboratory results were astonishingly excellent. His physical strength and stamina are extraordinary," the letter said.

"If elected, Mr Trump, I can state unequivocally, will be the healthiest individual ever elected to the presidency."

Dr Bornstein told NBC News the characterisation of "healthiest" was "black humour".

Mr Trump read out the language as Dr Bornstein and his wife were driving across Central Park, the doctor told CNN.

The campaign released the letter in December 2015.

"[Mr Trump] dictated the letter and I would tell him what he couldn't put in there," he said.

Dr Bornstein had previously said he had written the letter in a rush while seeing other patients.

His latest version of the letter's origins follows his accusation that Mr Trump's ex-bodyguard Keith Schiller raided his office while retrieving Mr Trump's medical records after he was elected president.

White House spokeswoman Sarah Sanders told reporters the records were retrieved as part of "standard operating procedure".

"As is standard operating procedure for a new president, the White House Medical Unit took possession of the President's medical records," she told a regular news briefing.

Asked if the operation was a raid, she said: "No, that is not my understanding."