Wikipedia is following in the footsteps of online retailer Amazon and blocking targeted advertising system Phorm from tracking visitors to its site.

Phorm's controversial service, known as '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.

Amazon's announcement this week came after the Open Rights Group (ORG) contacted a number of big tech companies including Amazon and Microsoft asking them to ban the service, as the ORG feels Webwise illegally intercepts web users' communications and could commit long-term damage to the brands that adopt it.

In a blog, the Wikimedia Foundation, which runs the online encyclopedia, said: "After some internal discussion on whether opting out of the Phorm user-profiling system in the UK would legitimise it, we're going ahead and requesting an opt-out for all the domains under the Wikimedia Foundation's control".

The blog also detailed the letter sent by Wikimedia's chief technology officer Brion Vibber to Phorm, asking to opt-out of the service. Vibber said: "We consider the scanning and profiling of our visitors' behavior by a third party to be an infringement on their privacy."

Jim Killock, executive director of the ORG, said in a blog: "We'd like to thank Wikipedia and Amazon for prioritising their users' privacy and taking this stand. We hope Facebook, AOL, Bebo, MSN, Google and others can follow their lead".