BT has completed its trial of controversial targeted advertising system, Phorm, which tracks users' online surfing habits raising privacy concerns.

The trial, which started on 30 September this year, saw around 10,000 BT Total Broadband customers invited to try the service through a web page that appeared as soon as they opened their browser. The web page also offered users the chance to switch the service on or off.

The Phorm Webwise system tracks users' online surfing habits and then delivers adverts relevant to the user. According to Phorm, BT had "achieved its primary objective of testing all the elements necessary for a larger deployment, including the serving of small volumes of targeted advertising".

The two companies will now analyse the results of the trial and make any necessary changes before the service rolled-out nationally to all BT customers.

The trial of Phorm is not the first held by BT. The ISP came under fire after it was revealed in April that it had held secret trials of the service, tracking more than 30,000 users in two separate tests that took place in 2006 and 2007.

Following a number of complaints about the trial, the Crown Prosecution Service is collecting evidence to establish whether BT illegally tested the Phorm online advertising system without users' consent.

Virgin Media and the Carphone Warehouse are also planning to trial the service, although no dates have been released yet.

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