New York's attorney general says that Tagged.com stole the identities of more than 60 million internet users worldwide - by sending emails that raided their private accounts.

Andrew Cuomo said he plans to sue the social networking website for deceptive marketing and invasion of privacy.

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"This company stole the address books and identities of millions of people," Cuomo said in a statement. "Consumers had their privacy invaded and were forced into the embarrassing position of having to apologise to all their email contacts for Tagged's unethical - and illegal - behaviour."

Started in 2004 by Harvard math students Greg Tseng and Johann Schleier-Smith, Tagged calls itself a "premier social-networking destination." The California-based company claims to be the third-largest social networking site after Facebook and MySpace, with 80 million registered users.

Cuomo said Tagged acquired most of them fraudulently, sending unsuspecting recipients emails that urged them to view private photos posted by friends.

The message read: "(name of friend) sent you photos on Tagged."

When recipients tried to access the photos, Cuomo said they would in effect become new members of the site - without ever seeing any photos.

Recipients' email address books would then be lifted, the attorney general said.

Tagged temporarily suspended its online campaign last month, in response to user complaints.

Email and telephone messages to the company were not immediately returned.

"This very virulent form of spam is the online equivalent of breaking into a home, stealing address books, and sending phony mail to all of an individual's personal contacts," Cuomo said.

The system was set up so that a user was asked whether the sender of the photos was a friend, then suggesting that if the recipient didn't respond, the friend "may think you said no" (accompanied by a sad face icon).

Any click resulted in the same thing, Cuomo said: Every person on a user's contact list received an email that again read, "(name of user) sent you photos on Tagged." The site then released a flood of offers for everything from sweepstakes to other services.

By the time a recipient realised there were no photos, it was too late.

Yesterday, a box on the site's home page still read: "NOW HIRING ... click here."

The attorney general said a lawsuit would seek to stop Tagged from engaging in "fraudulent practices" and to seek fines.