Hollywood director Bryan Singer has been accused in a lawsuit of sexually assaulting a 17-year-old boy at a party more than a decade ago.

The civil lawsuit, filed in Seattle, claims Singer demanded sex from Cesar Sanchez-Guzman during a 2003 yacht party.

After the then-teenager refused, the lawsuit claims, Singer pushed him on the bed and sexually assaulted him.

A representative for Singer said in a statement to the Associated Press that he "categorically denies these allegations and will vehemently defend this lawsuit to the very end".

He also threatened to file a malicious prosecution lawsuit on Singer's behalf.

The representative said: "Cesar Sanchez-Guzman apparently claims that he did not remember this alleged incident from 2003 until now."

Singer directed Superman Returns and several "X-Men" movies.

In the court filing Guzman claimed the alleged incident left him with "severe psychological, mental and emotional injuries".

It is the latest in a wave of sexual harassment and abuse allegations against powerful men in the entertainment industry, media and politics that began in October with accusations against Harvey Weinstein.