The hacking group LulzSec is rumoured to have intercepted the results of the 2011 UK census which includes some 25 million British households.
“We have blissfully obtained records of every single citizen who gave their records to the security-illiterate UK government for the 2011 census," a statement on pastebin attributed to the group said.
"We're keeping them under lock and key though so don't worry about your privacy (until we finish re-formatting them for release).
“Myself and the rest of my Lulz shipmates will then embark upon a trip to The Pirate Bay with our beautiful records for your viewing pleasure!”
LulzSec in a Tweet compared itself to whislebower site WikiLeaks.
"Thank you to the supporters who have assisted in leaks. Like @WikiLeaks, our sources remain anonymous. Leak payloads are being decided now."
While details are unconfirmed, Census information could contain income levels, employment information, statements on religion, as well as names and addresses.
Rik Ferguson, director of security research at Trend Micro, said: “No details are included in the statement regarding how the information was obtained, but the messages posted so far seem to indicate a leak rather than an intrusion or hack.
“This could undermine the confidence of the nation and possibly others to hand over sensitive information to a civil service that has already once demonstrated their inability to encrypt or safeguard it. Currently refusal to fill in a census is a criminal offence in the UK, will we be looking at mass criminality when the next census rolls around?”
Yesterday LulzSec said that it was declaring immediate and unremitting war on the ‘freedom-snatching moderators of 2011', calling its actions ‘Operation Anti-Security'. It also called for supporters to ‘open fire on any government or agency that crosses their path'.
It said: “We fully endorse the flaunting of the word ‘AntiSec' on any government website defacement or physical graffiti art. We encourage you to spread the word of AntiSec far and wide, for it will be remembered. To increase efforts, we are now teaming up with the Anonymous collective and all affiliated battleships.”
The Office of National Statistics said it is aware of news of the potential hack but is "working with security advisers and contractors to establish whether there is any substance" to the claims.
"The 2011 Census places the highest priority on maintaining the security of personal data. At this stage we have no evidence to suggest that any such compromise has occurred."
Update: LulzSec in a Tweet appeared to have refuted the claim that it stolen the Census database.
"I'm not seeing 'we hacked the UK census' on our twitter feed or website" it said.
With Darren Pauli.