It was merely a matter of time: Twitter, the latest social networking phenomenon, appears to have sparked its first libel action. And perhaps inevitably, singer Courtney Love, well known for sounding off online, is at its centre.

Fans of Twitter say its beauty is that it allows users to upload their thoughts as and when they think of them. This can be a serious disadvantage for those of a belligerent disposition. Ms Love's angry "tweets" against her former fashion designer, Dawn Simorangkir, have landed her in court.

According to a libel claim lodged by Simorangkir in Los Angeles Superior Court last Thursday, the widow of Nirvana frontman Kurt Cobain has carried out "an obsessive and delusional crusade" of malicious libel against her on Twitter, adding insult on MySpace and other websites.

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The designer, who lives in Austin, Texas, also claims that numerous tweets posted by Love on Twitter accuse her of being a "nasty, lying, hosebag thief"; having "a history of dealing cocaine"; having "lost all custody of her child"; and, being guilty of "assault and burglary". The singer adds that the designer would be "hunted til your [sic] dead".

Love then allegedly posted on a fashion site where Ms Simorangkir sells her clothes: "The nastiest lying worst person I have ever known ... evil incarnate, vile horrible lying bitch."

Ms Simorangkir is seeking punitive damages, arguing that the comments have destroyed her reputation and her business. Court papers laying out the claim state: "Whether caused by drug-induced psychosis, a warped understanding of reality, or the belief that money and fame allow her to disregard the law, Love has embarked on what is nothing short of an obsessive and delusional crusade to destroy Simorangkir's reputation and her livelihood."

Love turned against her, says the designer, after she billed the singer in February for around $4,000 of clothes she had made for her. Before that, Love had been buying ready-made items from the fashion website on which Ms Simorangkir trades. Love contacted the designer and flew her to Los Angeles last November and in January to give her bags of remnants to turn into bespoke garments.

The court documents say Love was furious that Ms Simorangkir stopped working for her after Love failed to pay her bill; this led to "an intense level of animosity ... well beyond what any reasonable person would consider acceptable behaviour". Love was not available for comment last week.

The case highlights the perils of celebrity blogging. Famous people such as Jonathan Ross, Stephen Fry and even President Barack Obama have embraced Twitter because it lets them communicate with fans and supporters without involving the media. Texts of 140 characters can be sent and uploaded in almost real time. But many celebrities, including President Obama, now use ghost-writers to update tweets.