Billy Bush has accused Donald Trump of "indulging in some revisionist history" for reportedly telling allies it was not his voice captured on a tape boasting of grabbing women by the p****.
"Of course he said it," the former host of NBC's Today programme, who lost his job as a result of the 'p****gate' scandal, said in an editorial published in The New York Times on Sunday.
"Along with Donald Trump and me, there were seven other guys present on the bus at the time, and every single one of us assumed we were listening to a crass stand-up act. He was performing.
"Surely, we thought, none of this was real. We now know better," Bush wrote.
The 2005 recording of the lewd conversation was made while Bush was the host of Access Hollywood and Mr Trump was a guest.
Mr Trump, then a tycoon and reality TV star, was caught on a microphone telling Bush about a woman he once tried to seduce, as he arrived on the set of daytime soap opera Days Of Our Lives for a cameo.
He is heard saying: "I did try and f*** her. She was married.
"I moved on her like a b****, but I couldn't get there."
He also bragged about women letting him kiss and grope them because he is famous.
Mr Trump said: "I just start kissing them. And when you're a star they let you do it.
"Grab them by the p****. You can do anything."
When the tape leaked before the presidential election in 2016 it sparked outrage.
Mr Trump later apologised for what he said and acknowledged it was "wrong", but dismissed it as "locker room talk".
Bush laughed on the recording as Mr Trump spoke. He lost his job after the tape was leaked.
He said at the time: "Obviously I'm embarrassed and ashamed. It's no excuse, but this happened 11 years ago – I was younger, less mature, and acted foolishly in playing along. I'm very sorry."
Towards the tail end of last year's presidential race, several women came forward and accused Mr Trump of sexually assaulting or harassing them over the years. He denied all the allegations.
Bush said he believed the women, and he was compelled to pen the piece following reports the US President had privately suggested the recording was not authentic.
"This hit a raw nerve in me," he wrote.
"I can only imagine how it has reopened the wounds of the women who came forward with their stories about him, and did not receive enough attention.
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"This country is currently trying to reconcile itself to years of power abuse and sexual misconduct. Its leader is wantonly poking the bear."
Responding to reports of Mr Trump's denial that it was his voice on the tape, White House spokeswoman Sarah Sanders said: "The President hasn't changed his position. I think if anything that the President questions, it's the media's reporting on that accuracy."