Dominique Strauss-Kahn 'guilty' of sex assault – but escapes shame of a trial

French prosecutors said yesterday that Dominique Strauss-Kahn was guilty of a sexual assault on a young French writer in 2003 but cannot be tried because the offence is more than three years old. A complaint for the more serious crime of attempted rape, brought by Tristane Banon, 32, was rejected because of a lack of evidence.

The rulings end all possibility of criminal charges against the former International Monetary Fund's managing director on both sides of the Atlantic. But they brand the French politician, in effect, as a self-confessed sexual aggressor who cannot be tried because of a technicality.

Ms Banon, goddaughter of DSK's second wife, came forward in July when the IMF chief had already been accused of the attempted rape of a chamber-maid in New York. The American charges were dropped in September.

The writer accused the former French finance minister, 62, of behaving like a "chimpanzee in rut" and trying to rape her in Paris in February 2003. She said that he wrestled her to the ground and tried to undress and fondle her. Mr Strauss-Kahn said that the accusation was "imaginary" and brought a suit against Ms Banon for defamation.

But the Paris state prosecution service said that Mr Strauss-Kahn had "admitted" sexually assaulting Ms Banon when he was questioned by detectives last month. DSK reportedly told investigators that he made "advances" to the young woman and tried to kiss her but stopped when she protested.

Since a prosecution for sexual assault (a misdemeanour) has to be brought within three years under French law, the prosecution service said that no action would be taken. Ms Banon's more serious accusation of "attempted rape" (a felony) can be prosecuted for up to 10 years. But the prosecution service said that it was dropping the rape investigation "for lack of sufficient elements of proof".

The statement continued: "Behaviour amounting to sexual aggression has been admitted. However, since the offence occurred in 2003, and was not revealed until 2011... the three year statute of limitations on misdemeanours of this kind has beenexceeded." The prosecutors said the attempted kiss was sexual assault but that the rape accusation was a case of "one person's word against another".

The decisions are a relief and a humiliation for Mr Strauss-Kahn. He still faces possible civil action by the New York chambermaid, Nafissatou Diallou. And the prosecution service said the man who denied ever forcing himself on women in a French TV interview last month, admitted that he behaved in a "sexual aggressive" way towards a woman nearly 30 years his junior.

Ms Banon's lawyer, David Koubbi, said yesterday that DSK would forever have to live with the label of "unjudged sexual aggressor". Mr Strauss-Kahn's lawyer, Frédérique Beaulieu, said that his client had been "totally vindicated".

Extracts began to leak yesterday from an "instant book" written by Ms Banon in which she gives her side of the story without mentioning Mr Strauss-Kahn by name. In Le Bal des Hypocrites (The Hypocrites' Ball), she speaks of being attacked by a "pig" and a "human baboon".

Ms Banon says that her life was destroyed by the incident. For eight years, her private and romantic life has been "chaos". Since that day, she said, there have been "too many men, too well known, too young, too old".

DSK's hopes of rebuilding his political career in France have been severely damaged.