LONDON • A party fell flat for a backup singer when the host, billionaire Richard Branson allegedly sexually harassed her.

Antonia Jenae, 44, first posted about the 2010 incident - at a party on his private island of Necker in the British Virgin Islands - on Facebook before sharing more details with The Sun.

She claimed that Mr Branson, now 67, stuck his head between her breasts.

Jenae, who was part of British singer-songwriter Joss Stone's backup group, said they had been invited to visit the island after a concert.

"Joss and I were like, 'What the hell was that?' Everyone was wondering why I wasn't angry because I'm usually a firebrand. But I was just too shocked," said Jenae about the alleged molest.

She added that Mr Branson also tried to get her to show him her breasts and walk around topless.

A spokesman for Mr Branson said no one had seemed upset after the party.

"Richard has no recollection of this matter. Neither do his family and friends who were with him at the time.

"There would never have been any intention to offend or make anyone feel uncomfortable. Richard apologises if anyone felt that way," the spokesman added.