Doug Gotterba - who worked for Travolta in the 1980s - recently sparked controversy by claiming in an interview with the National Enquirer that he had an affair with the actor.
Gotterba has now alleged that he received a threatening letter from Travolta's attorney Marty Singer following the article's publication but insists that he never signed a confidentiality agreement, TMZ reports.
He is reportedly suing Travolta on the grounds that he has done nothing wrong as he never signed a gagging order, adding that he should be able to talk about the Grease star.
However, Singer has claimed that the case is "ridiculous" and alleges that Gotterba did sign an agreement, adding that the pilot actually included the papers in his lawsuit.
"Mr Gotterba obviously filed this lawsuit to get his 15 minutes of fame," he said. "We plan to get this meritless case promptly dismissed."
Travolta was the subject of a series of allegations about his sexual conduct earlier this year, but has denied all wrongdoing. He also denied rumours that he paid off his accusers and was cleared of defamation by a judge in September.
Meanwhile, Kirstie Alley recently insisted that the actor is not gay, saying: "I think in some weird way, in Hollywood, if someone gets big enough and famous enough, and they're not out doing drugs and they're not womanising, what do you say about them?"