THE Guardian's ABCe topping website has been infiltrated by a "sophisticated and deliberate hack" according to an email being circulated tonight.
It was feared the personal information of thousands of users may have been compromised by the incident which the alert claims is now being investigated by the Metropolitan Police specialist e-crime unit.
According to the email, which comes from address ending guardianmailco.uk, the website "has been targeted by a sophisticated and deliberate hack which has breached the security of the data on the site."
"We are absolutely committed to the privacy of our users, and would like to assure you that we are treating this situation with the utmost seriousness."
"The matter has been reported to police who are now undertaking a full investigation through the police central crime unit at New Scotland Yard."
It adds: "The supplier who runs the site has identified the manner in which it was hacked and taken steps to prevent a recurrence."
"We have no reason to believe that any financial or bank date was compromised in this incident.
"However the police advise that those whose personal data may have been stolen in this way should take a number of precautionary measures."
It then provides links to a number of websites including the Met Police and details other agencies such as Equifax and Experian as ports of call.
The breach comes just days after the organisation's media site stated: "Guardian reclaims top spot with record figures of just under 33 million unique users".
Celebrating the success, director of digital content Emily Bell said: "Both our global and UK success can be attributed to our sustained investment in web content."
"The newly launched environment site attracted a significant number of new users and our TV site, offering user-friendly listings, has encouraged repeat visitors and increased engagement."
Such engagement can include signing up for news updates, football gossip, jobs alerts, media briefings, reader officers and money news among others, registering such personal details such as emails addresses postcodes, CVs, and names.
The jobs and careers section was one of the areas affected by the deliberate hack where, among others, current advertisers include MI6 – the Government's specialist anti-terror unit of international spooks.