ISP TalkTalk has also broken off its agreement with Phorm, the controversial system used to target advertising based on individuals' Internet surfing habits.

BT, a key player in the development of Phorm's Webwise system, announced earlier this week it would dump the company.

Phorm's service, Webwise, tracks users' online surfing habits and then delivers relevant adverts. Despite claims by Phorm that it 'anonymises' the information about web users so they are impossible to identify, the service has attracted a number of concerns from privacy campaigners, in particular, the Open Rights Group, which contacted big tech companies including Amazon and Microsoft asking them to ban the service.

The ORG said it felt Webwise illegally intercepts web users' communications and could commit long-term damage to the brands that adopt it.

Following the ORG's plea, both Amazon and Wikipedia announced they would stop Phorm from tracking users' activities on its web pages.

Phorm is also being investigated by the All Party Parliamentary Communications Group (apComms), as part a larger inquiry into internet traffic and the role of the government in regulating ISPs.

Unlike BT, which has actually trialed the service, TalkTalk had only had an agreement with Phorm and had no implemented any trials. Virgin Media also has an agreement with Phorm.

However earlier this year, the denied it planned to ditch the service.

We are investigating the use of Phorm's technology under our existing agreement with the company but, due to the complexities of the proposition, we do not have any timescales on when, or if, we will progress to trial or launch," said a spokesman for Talk Talk.