Mark Sweney in the UK newspaper The Guardian reports that the WPP one of the largest marketing and advertising business groups, has pulled advertising from more than 2,000 web sites that it believes carry pirated content.

The US division of GroupM, WPP's media planning and buying operation, spends about $3.5bn (£2.1bn) annually on buying ad space on websites on behalf of clients such as Ford, Unilever, AT&T and IBM.

This list, which will be expanded over time as many pirate sites are known to "domain hop", will eventually be expanded to encompass GroupM's global operations.

GroupM is responsible for about $6bn a year of digital media spend on behalf of its global clients, according to media evaluation company Recma.

The move could become a trend if other large media buyers demand similar services. It could also be a savvy way for WPP to cozy up to large media companies in Hollywood and elsewhere.

WPP said that the list will be expanded.