A long and expensive libel action against the parent (assuming he or she can be identified) might eventually result in compensation and an injunction, but it would give the libeller their day in court and the publicity they might well crave. And it might be difficult to enforce an award of compensation or costs against them.
Also, the courts are rarely persuaded to grant an immediate injunction to prohibit publication. To defeat an application for an injunction, the libeller does not have to prove their defamatory statement is true; they generally only have to say they intend to attempt to prove it is true.
One alternative is to go for the internet service provider. It is usually possible to report inappropriate use to the ISP by email, and they might close down a site if they think they are vulnerable to legal action.
The liability of ISPs is complex, but under the Defamation Act 1996 and the Electronic Commerce (EC Directive) Regulations 2002, they will not be liable if they are deemed a "mere conduit". So you cannot sue BT if one of its customers sends a defamatory email, any more than you could if he or she made a defamatory telephone call.
But if the ISP acts as a "host" and has some control over the content - as with blogs, forums, petitions etc - they can be liable if, having been made aware of the defamation, they do not act quickly to remove it.
But even then it isn't straightforward. Many hosts are based in the United States, where ISPs have greater protection and can shelter behind the First Amendment.
And there are many potential hosts. Once Microsoft had closed down the libeller mentioned above, he opened a new site hosted by Google, which we are now trying to close.
Simon Thomas, Solicitor, National Association of Head Teachers.