Documentaries critical of US government policy and big business interests will find it increasingly hard to get US network broadcast slots, despite a growing demand from the public, says leading author and professor of law, Joel Bakan.

Bakan, who wrote the book on which Mark Achbar and Jennifer Abbott's Joris Ivens' competition entry The Corporation is based, said that while publisher's were eager to back controversial books such as Michael Moore's best seller Dude, Where's My Country', documentary-makers were finding it tough to find US network slots because broadcasters are too afraid of alienating advertisers.

At a IDFA discussion on its USA Today programme, Bakan said : "Book publishing is a user-pays system but broadcasting is advertising-driven. That's what creates this bottleneck."

US film-maker Paul Devlin, whose award-winning film Power Trip, about the mixed fortunes of a US corporation's attempts to reform the Republic of Georgia's archaic power supply infrastructure, added: "It's definitely harder to get films out in our country.'

The situation is ironic because there is a growing demand for more contentious 'alternative' films from US cinema audiences. The growing interest in theatrical documentaries is demonstrated by the box-office success of Michael Moore's Oscar-winning Bowling For Columbine and Spellbound. US style magazine Vanity Fair is to publish a major feature on US 'documentarians' in its forthcoming Oscars issue in February.

Distributor Joe Rofekamp from Films Transit International said that with just two publicly-funded broadcasters in the US, getting networks to show controversial films was an uphill battle. Rofekamp added that the fact that many of the media corporations themselves were in the firing line didn't help. Fox was one of the media organisation under the spotlight in Achbar and Abbott's The Corporation, where two investigative journalists recount how Fox News pressured them into killing a cancer story about BST, a drug produced by GM food giant Monsanto. Achbar told IDFA Screen Daily: "There were a lot of pitches, a lot of interest and a lot of paperwork, but it was rejected by all for-profit broadcasters."

Despite the box office success of theatrical documentaries, a lack of support from broadcasters and major distributors has seen film-makers resorting to their own promotion and distribution strategies.

Bill Siegel, co-director of USA Today film The Weather Underground about an underground 1970s radical group, told IDFA delegates that he hired a full-time activist to promote his film to non-mainstream audiences. Devlin added that he made more money by holding onto video rights to his 1998 film Slamnation as he was able to sell the film at $250 a copy.