The Irish privacy regulator is to investigate how Facebook handles users' data across Europe. He will conduct the audit on behalf of authorities in 27 European states, including the UK.

The wide-ranging privacy audit at Facebook's Dublin premises will be launched in the next two weeks after complaints about how the network tracks its users online.

The commissioner expects to complete the report before the end of the year, a spokeswoman told the Guardian..

Facebook is under the privacy spotlight after changes made last week to how it stores information about its 800 million users round the world.

A spokeswoman for the commissioner said the Facebook probe would be its "most intensive" to date, due to the network's popularity.

The Irish regulator made his move after getting received 22 separate complaints from the online watchdog Europe versus Facebook since 18 August.

Facebook says one complaint about deleted information most likely relates to users' removing a post from a part of the social network without fully deleting it.

In the US the question has been raised of whether Facebook might be able to continue tracking your online activity afer you have signed off. Lawmakers and consumer advocacy groups in America are demanding a federal investigation into the issue..

Two congressmen have written to to the Federal Trade Commission saying that Facebook’s use of “cookie” software in this way should be investigated as an “unfair and deceptive act."

Congressmen Edward Markey, a Massachusetts Democrat, and Joe Barton a Republican from Texas, wrote, “When people log out of Facebook, they are under the expectation that Facebook is no longer monitoring their activities. We believe this impression should be the reality.”

On Thursday, the Electronic Privacy Information Center and nine other consumer and privacy groups made a similar request. The FTC declined to say if it plans to investigate. "The calls for action add to growing criticism of the world’s largest social-networking site and its privacy policies," said the Washington Post.

Australian hacker Nik Cubrilovic, who looked into Facebook’s code and discovered that the network was apparently tracking users’ Web consumption after they logged off. He posted this discovery on his blog last Sunday. Cubrilovic said Facebook explained that the company has cookies that persist after log-out to identify outside parties who try to access a user’s account.

Later Facebook engineer Gregg Stefancik in a statement acknowledged that Facebook, like other Internet sites that personalise content, uses cookies. Three of these cookies on some users’ computers “included unique identifiers when the user had logged out of Facebook. “However, we did not store these identifiers for logged-out users. Therefore, we could not have used this information for tracking or any other purpose,” Stefancik said.

Facebook said the issue has been fixed so the cookies would not retain the identifiers.