Colin Firth's box office hit The King's Speech is at the heart of a landmark court battle over online piracy between Hollywood film giants and Britain's largest internet service provider, BT.

Major film studios, including Paramount Pictures and Disney, asked the high court in London on Tuesday to force BT to block access to the website Newzbin2, which they claim is "infringing copyright on an enormous scale" – including 75 illicit versions of The King's Speech.

The case is the first of its kind in Britain and could pave the way for the biggest clampdown on online piracy yet.

Hollywood studios argued in court that illicit filesharing was a "very significant social evil" and is responsible for "several hundreds of millions of pounds a year" in lost revenue. The studios – represented by their international trade body, the Motion Picture Association (MPA) – want BT to cut off access to Newzbin2 for UK internet users in the same way that it blocks child abuse websites on the Internet Watch Foundation (IWF) list.

However, BT claims that such a blocking order would be the "thin end of the wedge" and there would be "nothing to stop countless other" rights holders demanding that hundreds of other contentious websites are banned.

In its skeleton argument, BT claimed in the high court that rights groups would like to see about "400 sites a year" blocked by internet providers. "Rights holders in the music and movie industries have already identified 100 copyright infringing websites which they would like to see blocked," the ISP said. "Claimants would seek orders blocking access to websites alleged to contain defamatory allegations or private and confidential information."

Richard Spearman QC, acting on behalf of the film studios, told the court that if a blocking order is granted, they will demand that other UK ISPs, including TalkTalk and Virgin Media, also blacklist the website or face court action.

He told the court that there was now "no other way of impeding the infringement of copyright" than to obtain a court order. "[Newzbin2] allows repeat and mammoth-scale copyright infringement," Spearman said. "If BT could not see that happening then they have to be the biggest ostrich in history."

The offshore-based Newzbin2 has about 700,000 members, with annual turnover of more than £1m, according to the rights holders.

According to the rights holders, Newzbin2 currently helps distribute about 115,000 illegal versions of films and 320,000 TV shows.

The film industry's fight against Newzbin stretches back to March last year, when the high court ordered the offshore-based site to remove all of its pirated material and pay damages to the studios.

However, the company behind the site, Newzbin Ltd, went into administration shortly after the ruling and avoided compensating the studios. Within weeks, clone site Newzbin2 appeared hosting similar material. The rights holders claim Newzbin2 has about 700,000 members, with an annual turnover of more than £1m.

Chris Marcich, the MPAA president for Europe, the Middle East and Africa, said: "Newzbin has no regard for UK law and it is unacceptable that it continues to infringe copyright on a massive and commercial scale when it has been ordered to stop by the high court."

The case continues and the high court is expected to make a ruling this week.