Police are investigating the woman, who has not been officially named, for a suspected breach of Iran�s strict morality laws forbidding sex outside marriage. Unmarried people who break the law are subject to punishment by lashing.

Investigators have also asked Interpol to arrest and extradite the woman�s male partner, who is thought to have fled to Dubai.

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The man is suspected of distributing the explicit film, which may have been shot using a camcorder with the woman�s consent.

If convicted, he faces up to three years in jail and a �6,000 fine.

However, the biggest impact could be on his partner�s hitherto burgeoning screen career. The actress, who is in her mid-20s, appeared destined to land more roles in television dramas and Iran�s small but lively film industry after her role in a popular soap opera. But the stigma of sexual scandal now makes that unlikely.

Stringent Islamic rules preclude even cursory touching between men and women in Iranian productions, while foreign programmes and films are rigorously censored for illicit inter-gender contact.

The incriminating film is believed to be two years old but began circulating as a DVD and on some websites a few weeks ago, titillating a public starved of the celebrity gossip common in western media.

It came to the attention of the morals police, who are charged with enforcing Iran�s Islamic laws.

Police said they have not established a motive for the film�s distribution. Tehran�s chief prosecutor, Saeed Mortazavi, has ordered a �special investigation�.

Tehran�s police chief, Brigadier-General Ahmadreza Radan, told reporters that the film�s participants would also be subject to prosecution.

Police have banned the naming of those involved.

News of the case has prompted a flurry of speculation that the actress attempted suicide after her interrogation.

However, she told the ILNA news agency: �I just want to tell my country�s people that I am alive. I should think of Iranian women�s strength and defend the respect of the girls and women of my nation.�

The illegal copying and distribution of private films and pictures of local celebrities is a growing trend in Iran, sometimes with serious consequences for the subjects.

In one instance, a television presenter was fired by the state broadcasting company after being filmed dancing with the bride (to whom he was not related) at a wedding.