The personal details of hundreds of thousands of Sun newspaper readers have been posted on the web by a hacker, according to Computerworld UK sources.

The hacker claims not to be affiliated with hack attack groups LulzSec or Anonymous. The news follows an attack last month that saw hackers breach the company’s content management systems and post a fake story on The Sun’s website that proprietor Rupert Murdoch has been found dead.

The details posted online are understood to include home addresses, email addresses and phone numbers. They have been placed on a number of popular filesharing websites.

The hacker, named as Batteye, said he had also posted the details of people who had entered competitions with the newspaper, or posted comments on the paper’s website.

“It's amazing how much info can be kept in the one place.. Names, Emails, Addresses, Mobile numbers...” said the hacker. He claimed that other details included a list of people who said they had been bullied at school, as well as entrants in recent editions of the annual Miss Scotland beauty pageant.

Batteye indicated he was not part of Anonymous, but supported their cause. “I'm not really with anonymous... but then again I sort of am, aren't I?” he wrote on Twitter.

News International said in a statement to The Times newspaper that it was tackling the problem. “We take customer data extremely seriously and are working with the relevant authorities to resolve this matter. We are directly contacting any customers affected by this.” It has not made any further comment.