X-Men director Bryan Singer has been hit with a second sexual assault lawsuit, this time from an anonymous Briton who alleges that when he was 17 he was abused by the film-maker at an afterparty for 2006's Superman Returns. Singer vehemently denies the fresh charges.

According to the Daily Beast, the teenager met Singer and Hollywood producer Gary Goddard at a London hotel where the film event was being staged. When he refused sex with Singer, a large musclebound man was brought to the room where he physically assaulted the teenager. Singer then allegedly attempted to penetrate the 17-year-old Briton.

According to the suit, the plaintiff "only recently became cognizant that he has suffered psychological and emotional injuries, mental anguish and loss of enjoyment of life as a result of the Defendants' sexual acts. Such injuries are severe, continuing, and permanent".

The lawsuit has been filed by Jeff Herman, who previously filed suits against Singer and Goddard, claiming they engaged in a Hollywood "sex abuse ring".

Plaintiff Michael F Egan III, who has waived his right to anonymity, claims he was abused by Singer, Goddard and others in Los Angeles and Hawaii as a 17-year-old during a period in which he was trying to make an acting career for himself in Hollywood. Herman, who handles sexual abuse cases across the US, has held several press conferences in Los Angeles to put forward his allegations.

Goddard, who directed the 1987 children's fantasy Masters of the Universe, is alleged to have groomed the anonymous British teenager after contacting him via social media.

Both Singer and Goddard have fiercely denied all allegations against them. Singer has withdrawn from publicity appearances for forthcoming superhero movie X Men: Days of Future Past while he fights the allegations.

Singer's lawyer, Marty Singer, told the Daily Beast that the allegations were "totally untrue".

"After the substance of Mr Herman's previous defamatory and fabricated filing in Hawaii was disproved based on unassailable evidence, Mr Herman's desperation has led him to fabricate these new anonymous accusations against Mr Singer, which we will also prove to be completely false," he said. "It is time for the media and public to focus their attention on Mr Herman's nefarious motives and tactics, which seem to be driven solely by his need to shake down an innocent man like Bryan Singer. We intend to seek sanctions against Mr Herman for his reckless, unethical behaviour."

Goddard's lawyers, Alan Grodin and Paul Gaspari, also issued a statement. "It is a sad indictment on society that when once spurious claims making false, serious and highly damaging allegations have been made – especially where compensation is sought – that other similar claims may follow," it reads. "The allegations made against Mr Goddard are vehemently denied and will be vigorously defended at any trial of these matters and Mr Goddard is entirely confident that he will be fully vindicated."