Hundreds of Twitter users have reacted to a footballer's bid to find out who is putting information about him on the website by posting new messages online.
The player, who an injunction says can only be identified as CTB, is taking action against ex-Big Brother star Imogen Thomas and the Sun newspaper.
He has now obtained a High Court order asking Twitter to reveal details of users who had revealed his identity.
Twitter has not commented but hundreds of users have repeated his name online.
'Fully entitled'Papers lodged in the High Court against Twitter and "persons unknown" request disclosure of Twitter users said to have published confidential details.
The order against the US-based micro-blogging website requires Twitter to disclose the requested information within seven days - or within the appropriate time required by the law in California, where it has its headquarters.
Lawyers at Schillings, who represent CTB, have issued a statement clarifying the action it has taken.
It said it was not suing Twitter but had made an application "to obtain limited information concerning the unlawful use of Twitter by a small number of individuals who may have breached a court order".
ANALYSIS
<!-- pullout-items--> <!-- pullout-body-->Once again Twitter finds itself centre stage in the debate over privacy.
Two weeks ago, one Twitter follower made a concerted attempt to challenge the law by pulling together, in a short burst of tweets, the names of celebrities thought to have taken out gagging orders.
Jemima Khan poured petrol on the flames by tweeting a denial, giving broadcasters and newspapers a legitimate peg to run the story.
Websites such as Twitter have put a huge strain on the ability of the courts to enforce gagging orders and it has been widely assumed there is no legal redress against them.
The Culture Secretary Jeremy Hunt said this week that digital media had made an ass of the law and it was hard to enforce injunctions against Twitter because it was incorporated in the United States.
Now it seems the law is about to be tested.
<!-- pullout-links-->It comes days after a High Court judge said the footballer was "fully entitled" to anonymity.
Justice Eady has reserved judgement on lifting the injunction after a private hearing with the man's lawyers, the Sun and former Miss Wales Imogen Thomas in London.
However, since news of the disclosure order became public on Friday hundreds of people have tweeted information revealing the footballer's identity.
One message being re-tweeted on the micro-blogging site, stated: "xx xx is suing Twitter. I can't Imogen why."
The legal move by the footballer comes two weeks after a Twitter user tried to unmask some celebrities who have obtained privacy injunctions to prevent publication of details of their private lives.
The Twitter user claimed to "out" a number of UK public figures, although the tweets appeared to contain errors.
Media commentator Steve Hewlett said CTB's lawyers were, in all likelihood, "trying to establish the real identity" of that user.
He said the privacy injunction preventing CTB's identity being revealed had been challenged on the grounds that it was already in the public domain because it was already available on the internet.
Mr Hewlett said "arguing that it's in the public domain because it's already on Twitter" would "put you in a very serious position in terms of contempt of court" if it transpired that "you had anything to do with putting it on Twitter".
There are precedents for legal action to find out the names of individuals behind some Twitter accounts.
'Everybody knows anyway'
Publicist Max Clifford told the BBC that while leaked information on Twitter has a limited impact, journalists can try to use it as leverage.
"It appears to be out of control. It's a strong bargaining chip as journalists want to say, 'Everybody knows anyway,'" he said.
Mr Clifford said some kind of balance must be struck to protect privacy and freedom of speech.
The publicist said: "Super-injunctions and injunctions are purely a law for the rich, and purely there to protect the rich.
"What you need is some halfway house between the invading of people's privacy and freedom of the press and information both of which are vital in a democracy."
Twitter has been resisting attempts by the US government to subpoena information on a number of users in relation to the Wikileaks affair.
Media lawyer Nick Lockett said the legal action against Twitter may not have much effect.
"What will have to be established is that Twitter was subject to the jurisdiction of the court," he said. While UK courts claim worldwide jurisdiction this has often proved hard to enforce.
In the case of the US, said Mr Lockett, the situation was complicated by the Communications Decency Act which grants immunity from prosecution for providers of "interactive computer services" under certain circumstances.
Lawyers acting for CTB may struggle to prove that Twitter does not deserve this immunity, said Mr Lockett.