Iranian prosecutors are investigating a video purporting to show young soap star Zahra Amir Ebrahimi making love to her boyfriend. Ebrahimi, known for playing wise and morally upstanding characters, has vehemently denied being the woman in the film but her career could be ruined over the scandal.
Her alleged partner in the video stands accused of breaking the law by distributing the material illegally and could face a year in prison.
The man, whose name was not given, has fled the country.
The actress described the events as an "immoral campaign" and denounced "unjust and dishonourable accusations aimed at trampling over the honour of a woman," according to the semi-official agency Ilna on Wednesday.
She has also moved to reassure her fans that rumours she has committed suicide are false.
The issue has now reached such a scale that Tehran's hardline chief prosecutor, Saeed Mortazavi, has resolved to personally handle the case.
"The prosecutor has ordered the arrest of the young man who fled the country and is now abroad," said Mortazavi's deputy, Mahmud Salarkia, according to the Kargozaran newspaper.
Seyed Nasser Seraj, a public relations official at the judiciary, said "a full report and a copy of the film have been sent to the prosecutor ... The results will be announced after the inquiry."
According to Iran's Islamic law, any person found guilty of encouraging prostitution, harming people's privacy or public morality faces jail. Any sexual relationship outside marriage is also illegal.
