The BBC is reviewing its editorial controls on the Celebdaq website message boards, after a footballer who had taken out an injunction preventing publication of a kiss n' tell story was named on the site.

BBC executives are today asking tough questions about how the offending messages, which could land the corporation in legal hot water, were allowed onto the website yesterday.

And today it emerged that the corporation does not check all messages for potential libel or offensive content before they are posted.

It operates a two-tier system of regulation - on sites such as BBC children's and the Asian network it intercepts all messages before they are posted but on others it doesn't check for libel or offensive content until after the messages are posted.

It appears this is the reason for a blunder that could land the corporation in the high court facing a contempt of court action.

The Celebdaq message board, on which people swap gossip and tips about celebrities who are likely to be in the news, is only "moderated" - edited - after people have posted their messages, a BBC spokeswoman confirmed.

An external agency, Chat Moderators, handles the after-post moderation of the message boards.

The spokeswoman said the BBC was reviewing whether all the Celebdaq boards needed to be moderated before users' messages were posted on the site.

"[These message boards] can be pre- or post- moderated. If they are pre-moderated, it slows down the site. This site had been post-moderated," she added.

The decision to moderate what goes out on the children's sites mirrors the 9pm "watershed" guidelines that operate in TV. And a decision to keep a closer guard on the Asian network message board would have arisen out of concerns about racism, particularly post September 11.

But the BBC could not say why Celebdaq, which actively encourages viewers to trade on celebrity gossip, was not moderated like its children's and Asian sites.

The BBC could face a costly legal battle over the Celebdaq message board postings.

A teacher last year won a libel action against school reunion website Friends Reunited over libellous allegations made by a former pupil in a test case that established that the internet is not outside the defamation law.

And last autumn gossip website Popbitch was forced to remove a rumour about David Beckham after being threatened with legal action from the footballer's legal team.

Two years ago internet service provider Demon paid more than £200,000 to settle a libel action over material posted on one of its newsgroups.

Demon refused to remove postings about physicist Dr Laurence Godfrey described by his lawyers as "squalid, obscene and defamatory".

The case, settled just four days before a jury trial was due to begin, hinged on whether an ISP could be deemed responsible for what went up on the website, as is a traditional publisher.

Demon argued at the time it had neither the resources nor expertise to monitor the content of hundreds of thousands of messages posted each day.

Media lawyers said the legal position of the BBC over the Celebdaq website leak was unclear, because internet libel was such a grey area of the law.

"Ostensibly the BBC is likely to be liable for a breach of an injunction committed by a third party using their system. However, this is an uncertain area," said Dan Tench, a media lawyer with Olswang.

"If the BBC can show it acted properly and took down the offending posts as soon as they were noticed, it's unlikely in this case that a court would seek to punish the BBC heavily," Mr Tench added.

"However, the courts may in future be looking at the steps that celebrity gossip sites take to discourage or prevent such material being posted."

Charles Boundy, a media specialist at legal firm Fladgate Fielder, added: "If the BBC admits some degree of editorial control over the website obviously it puts it at a higher degree of risk in terms of any defamation claim. And with the Celebdaq site, where it could be in the interests of punters to be indiscreet in the first place, the need for reasonable care could be regarded as heightened.

"Cases that have gone to court on internet libel have tended to be about ISPs, not content sites. Where there are new trends and no settled law there is a risk," Mr Boundy said.

"A court would undoubtedly have a good close look at this and could be making new law whichever way it jumped."