She isn't the first person to be accused of helping to assassinate JFK, but she may be the most glamorous: Katie Holmes, the actress better known as Mrs Tom Cruise, is at the centre of what Hollywood liberals are theatrically billing a sinister right-wing plot to destroy the late president's reputation.

Ms Holmes was unveiled last week as the star of The Kennedys, an eight-hour History Channel mini-series, in which she will play JFK's wife, Jackie. Greg Kinnear, an Oscar nominee, will portray the president, while the British actor Tom Wilkinson will take the role of his father, Joseph. The A-list cast has, however, been announced to a chorus of scepticism about the purpose of the high-profile show, which is scheduled to air on the US cable channel in the run-up to January's 50th anniversary of the charismatic Democratic president's inauguration.

Critics have claimed that the film's producers, who are led by Joel Surnow, the creator of 24 and one of the most prominent Republicans in Hollywood, are cooking up a historically inaccurate hatchet job that focuses on sex and scandal in an effort to destroy JFK's reputation. Several prominent historians have gone so far as to call on the public to boycott the film – the first drama the History Channel has ever produced – alleging that Surnow, a friend of the conservative talk-show host Rush Limbaugh, is using it to advance a revisionist political agenda.

A copy of the film's script was leaked earlier this year, revealing that executives at the TV station, which usually screens weighty documentaries, green-lit a project that attempts to portray JFK as an intellectually-challenged sex addict.

They are particularly upset by a scene in which a secret service agent spends several minutes trying to get President Kennedy's attention as he attempts sexual intercourse in a swimming pool with a woman called Judy, who is very much not his wife.

Another bone of contention is a line of dialogue in which Kennedy will tell a confidant that promiscuity is the only way that he can ward off headaches: "If I don't have some strange ass every couple of days, I get migraines."

Opposition to the film is being led by the left-leaning documentary-maker Robert Greenwald, who has now posted a video on YouTube in which historians and former Kennedy confidants ask viewers to sign a petition calling on the History Channel to have the script extensively rewritten. In the video, one of JFK's former confidants, Theodore C Sorensen, describes Surnow's script as "one-sided" and "right-wing", and says it "suffers from a vindictive, malicious approach". He adds: "Every single conversation with Kennedy in the Oval Office in which I, according to the script, am supposed to have participated, never happened."

The historian David Nasaw, meanwhile, uses Greenwald's film to complain that The Kennedys will "bear no relationship that I can see to the lives that these people lived ... This film is not only extraordinarily anti-Catholic. It's anti-Irish, in a way I have not seen in a long, long time."

A third critic, Nigel Hamilton, the British author primarily known for his biography on the young John F Kennedy, JFK: Reckless Youth, says that green-lighting the film represents ugly dumbing down by a channel that has previously been a home of serious historical programming. "It's a travesty. Why feed this kind of garbage on something called the History Channel?" he said. "Why not put that out on another channel and call it The Sex Lives of the Kennedys?"

For their part, defenders of Surnow would, quite understandably, argue that Greenwald and his chums are complaining too much. After all, JFK certainly did enjoy a colourful private life and has long been rumoured to have counted Marilyn Monroe among his many alleged mistresses.