Given the subject matter it is perhaps understandable why Outfoxed is one documentary going straight to DVD rather than to the cinemas. After all, it is one thing to upset George Bush and McDonalds but a whole more dangerous business risk to court Rupert Murdoch's displeasure.

Directed by Robert Greenwald, it is a shamelessly partisan expose of the way in which Murdoch's Fox News Channel has become little more than a Republican mouthpiece, brow-beating interviewees who don't subscribe to the party line, firing staff of the wrong political persuasion and, more scarily, distorting the news to present its version of the 'truth' to the American public.

Newspapers have, of course, always shown political bias but imagine if a British news presenter started badmouthing and ridiculing Blair or Howard during a supposedly objective news report. That's pretty much the situation with Fox where daily editorial content memos are issued to the staff outlining the political agenda for the day.

Basically, George Bush is great, Democrats suck, foreigners and liberals are the enemy. During the run-up to the elections, there was even a concerted effort to suggest John Kerry was French. Using interviews with media pundits and former employees who either jumped or were pushed, Greenwald unfolds stories that would be too implausible in a work of fiction.

A former presenter recalls being reprimanded for not making Reagan's birthday into a bigger story. News becomes misinformation spun to reinforce a climate of fear and therefore dependency on the president. Speculation and hearsay becomes fact by repetition. The son of a man killed in 9/11 is demonised during an interview for daring to question the war on Iraq.

All that plus a montage of sound bites that effectively lets Fox News bury itself while constantly chanting its hysterical official catchphrase-'Fair and balanced'.

Given there are no examples of practice from other networks to afford comparison and despite Murdoch's vast empire of print and TV media Greenwald focuses solely on Fox News. Balanced probably isn't exactly a term you'd apply to the documentary either.

But, then you wouldn't expect a documentary on Goebbels to be particularly even-handed either. It may have made and illustrated its point long before the end credits roll but it's a fascinating, and at times, a grimly funny piece of work which, if nothing else, goes a long way to explain why 67 percent of Fox viewers believed Saddam Hussain and al Qaeda to be connected.