Clooney caught in crossfire as war breaks out over latest film

The writer and journalist Jon Ronson must have been thrilled when he learned that George Clooney and Ewan McGregor were to be cast in a film inspired by his book, The Men Who Stare at Goats.

But, in advance of the nationwide premiere of the movie this Friday, Ronson's moment of glory is in danger of being tarnished by claims of betrayal by his one-time best friend and fellow documentary-maker, John Sergeant. Sergeant, 51, who has worked with Ronson for years, has accused him of "airbrushing" him out of the story, and is now seeking redress by taking his gripes straight to George Clooney, dragging the actor into the row.

He claims he spent two years in Los Angeles, from November 2001 to 2003, researching and gathering material for the TV series Crazy Rulers of the World, which was broadcast on Channel 4 in 2004, and from which Ronson's bestselling book was spawned. He says he found key figures on which the story was based, and persuaded them to speak on camera.

Ronson's work is a non-fictional account of the American government's attempt to harness paranormal abilities as part of a top-secret military programme. It is understood that Ronson signed a contract which allowed him to write a book based on the series and that the film rights were then sold.

Sergeant told The Independent: "I worked intensely through 2003 and 2004 on it." He said that, had the material remained within the context of a documentary, he would happily have let the matter go.

"I never formally agreed for the material I unearthed to be used in other media," he added, "and I was extremely uncomfortable when it was, especially when I was airbrushed out of things. Ewan McGregor is playing this character who finds the story. [Jon] presents that person as [himself] but really, it is me."

The film tells the story of a reporter (ostensibly Ronson) played by McGregor, who comes across a man named Lyn Cassady while searching for his next big story. Cassady, played by Clooney, claims to be part of an experimental US military unit which includes a band of "warrior monks" with the ability to read the enemy's thoughts, pass through walls and kill goats simply by staring at them (hence the film's peculiar title).

While Sergeant was credited in the book – which Ronson dedicated to him, and which included an afterword commending his research and guidance – the film makes no mention of his contribution. The film-makers state that the work is "inspired by Jon Ronson" but do not acknowledge Sergeant in any way.

When Sergeant was not invited to the film's screening at the London Film Festival on 15 October, he wrote to Clooney detailing his grievances and asked the festival's artistic director, Sandra Hebron, to pass on his letter to the actor's publicist, which she duly did. However, yesterday, Stan Rosenfield, Clooney's Los Angeles publicist, said: "George is not aware of any attempt to reach him."

Ronson declined to comment for legal reasons.