LONDON: UK telecoms giant BT is facing an investigation by the country's Crown Prosecution Service over allegations that its trials of a targeted online advertising system contravened privacy laws.

Tests of the Phorm-designed service, which tracks the websites visited by internet users, were run in 2006 and 2007, but BT did not ask customers' permission before running the trials.

Although an investigation by the City of London Police conducted earlier this year found that the tests were not illegal, the CPS has opened an investigation of its own after privacy campaigner Alex Hanff filed a private prosecution.

If BT is found to have broken the Regulation of Investigatory Powers Act, which prohibits the interception of online data without consent, the case will be referred to the Director of Public Prosecutions.

BT argues that it "sought expert legal advice in advance" before implementing the trials, and did not use the data accrued in an illegal fashion.

Says a spokesman: "Targeting advertising is a fast-growing area which offers real benefits to customers."

"Customers' IP addresses were not divulged and we did not have any way of knowing who was taking part in the trial."

Data sourced from; additional content by WARC staff