Donald Trump's campaign says the cousin of one of the women who has accused him of an unwanted sexual advance is "shocked and bewildered" by her account.

In a statement from Trump's campaign, John Barry of Mission Viejo, California, says Summer Zervos "wishes she could still be on reality TV, and in an effort to get that back she's saying all of these negative things about Mr. Trump".

Earlier on Friday, Zervos said at a news conference in Los Angeles that Trump kissed her and touched her breasts in a private room at the Beverly Hills Hotel in 2007.

At the time, Trump had recently married his third and current wife, Melania Trump, and the couple had an infant son.

Zervos was a contestant on Trump's reality TV show The Apprentice. Barry says Zervos often praised Trump after appearing on the show.

Berry said Zervos invited Trump to visit her restaurant earlier this year, and the Republican declined.

"Summer's actions today are nothing more than an attempt to regain the spotlight at Mr. Trump's expense," Berry said.

The latest accounts come after several women reported in recent days that Trump groped or kissed them without their consent.

At a campaign rally in North Carolina on Friday, Trump sought to discredit his accusers. He said because there were no witnesses to the interactions, the allegations were not credible.

"Right now I am being viciously attacked with lies and smears,'' Trump said at an outdoor amphitheatre. "It's a phony deal. I have no idea who these women are.''

In a statement released by his campaign, Trump denied he was ever alone in a hotel room with Zervos and claimed to have only a vague recollection of meeting her. He lashed out at the media for creating "a theatre of absurdity that threatens to tear our democratic process apart and poison the minds of the American public".