'Jackass 2.5', the third in the 'laddish' series of movies featuring Johnny Knoxville and copious amounts of nudity, is to become the first studio-backed feature film to receive its premiere on the web.

Paramount Pictures is hoping that it can open up a new stream of web-based revenue when it makes the one-hour plus film available free of charge in conjunction with Blockbuster's Movielink service on December 19.

Customers will have to watch several 15 or 30-second advertisements before being able to watch the movie, which will be streamed rather than downloaded.

The streamed version, which will be followed by a release on 'download to own' sites such as Amazon and iTunes a week later, is understood to be the first feature-length film to be released online before general release by a major studio.

Fox Searchlight and Sony have both experimented releasing films exclusively for the web, often as 'teasers' or as part of promotional campaigns, but only ever in short format.

The new film, which reportedly cost less than $2 million to make, will feature new material, as well as previously unseen outtakes from the second Jackass film, which made £1.7 million at the UK box office when it was released in 2006.

Viacom, Paramount's parent company, is also aiming to attract traffic to the jackassworld.com site, which offers archival episodes of the MTV 'Jackass' series from five years ago, and is being built by a fellow subsidiary, MTV Networks.

The film is not rated and the online version - which contains racy segments - will only sold with 'age verification technology' that attempts to ensure viewers are 17 or older.

Movie industry experts said that the film reflected a new desire on the studios' part to embrace the idea of releasing free, ad-supported content - partly as a consequence of their failure to prevent films being circulated on illegal file-sharing sites.

But, they said, it would also present an opportunity for low-budget films suited to small-screen viewing to bypass traditional distribution channels and appeal directly to their target audiences.

"In 10-15 years the idea of going to the cinema to see every film is going to seem quaint," Andy Lowe, an associate editor at Total Film magazine, said.

"Obviously some films - like Mission Impossible: 3 don't lend themselves to being watched on a small screen, but for many lower budget films which can't afford a big spend on distribution, this is the perfect mode of delivery."

The first Jackass film took just over $4 million at the UK box office when it was released in 2003 and the sequel, 'Jackass: Number Two', made only £1.7 million, according to Nielsen EDI.

Paramount executives said that the film's production costs would be recouped by a license-fee guarantee - understood to be in the low seven figures - that Blockbuster has paid for its one-week exclusive.

On December 26, the 'download to own' version of film will go on sale on iTunes and Amazon for between $10-15 and a DVD featuring 45 minutes of extras will also be available for $30.

In January other ad-supported streaming sites, such as Joost, will start showing the film, followed by a broader release through the video-on-demand services of cable and satellite networks in February.

Thomas Lesinski, president of Paramount Pictures Digital Entertainment, told The New York Times: "If this works, it could open up and really change the game about additional content that studios can create."

Fox and NBC already plan to make a range of archival material - including TV shows and some films - available in a free, ad-supported format via their Hulu.com website.

Film admissions in Britain are up 10 per cent year on year, with 138 million tickets having been sold to Britons so far this year, according to Carlton Screen Advertising.

Box office takings, however, are relatively static, with cinemas having taken just over £840 million in each of the past two years, Nielsen EDI said.

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