A one-time reality TV star has ruined U.S. President-elect Donald Trump's inauguration week by filing a defamation suit against him.

Summer Zervos, who appeared on Season 5 of Trump's reality show The Apprentice, has filed papers against him, accusing the property tycoon of defaming her at one of his campaign rallies by calling her a liar after she claimed he made inappropriate sexual advances towards her.

Zervos claims Trump kissed and groped her at the Beverly Hills Hotel in 2007.

Responding to her allegations and those of other women who attempted to discredit him, Trump said, "All of these liars will be sued after the election is over."

Zervos' attorney, Gloria Allred, announced the lawsuit during a press conference on Tuesday (17Jan17).

Allred, who is also representing several women accusing disgraced comedian Bill Cosby of rape told reporters Trump's remarks "knowingly, intentionally, and maliciously threw each of these women under the bus".

Trump will be inaugurated as America's 45th President on Friday (20Jan17).