Donald Trump has admitted he used aliases to promote his business affairs but still denies he impersonated his publicist to brag about himself during interviews in the 1980s.

The presumptive Republican nominee owned up to the trickery during an interview with the late-night chat show host Jimmy Kimmel on Wednesday.

"You know, over the years I have used aliases...I used the name Barron and made a very good deal using that name," he said, adding that it became the inspiration for the name of his own son, Barron Trump.

Despite this, two weeks ago Mr Trump denied ever using aliases during a TV interview where he was confronted with an audio recording of an apparent Trump publicist named "John Miller" whose voice sounded remarkably similar to his own.

"To me that didn't sound like my voice," he said and denied that he was infamous for impersonating his own press officers and publicists when speaking to reporters in New York in the 1980s.

In the bizarre audio recording, uncovered by the Washington Post, "John Miller" praises Trump as "a good guy [who] is not going to hurt anybody" and speaks at length about his great business acumen.