Demanding a ban on the film, Abdul Rashid Ghazi, deputy chief cleric of the mosque that has been at loggerheads with the government on several issues, has warned of serious consequences if a private TV channel is allowed to telecast the film.
He would not object, however, if a board that would include ulema - the Muslim priests - cleared the film, the cleric was quoted as saying in the Daily Times Tuesday.
Ghazi declared the film "blasphemous", meaning that it was derogatory to Islam and a punishable offence under Pakistani law.
"The film is against Islamic norms and traditions and is being released on a private TV channel without prior approval from a censor board. We won't allow this," said Ghazi.
"The government will be held responsible if the film is released without being censored," he said. The film - produced by Shoaib Mansoor - is scheduled to be released here on July 7.
Ghazi and his brother, Maulana Abdul Aziz, have been daring authorities for the last six months after capturing a part of a girl's seminary. The government says the students - both boys and girls - are trained and armed.
President Pervez Musharraf last week said the militants ensconced inside have connections with the Al Qaida and belong to Jaish-e-Mohammed (JeM), engaged in terrorism in Jammu and Kashmir since the 1990s.
Lal Masjid was in the news for abducting Chinese workers, including women, at a massage parlour that it said was doubling up as a brothel.
Earlier, its fatwa forced out the country's Tourism Minister Nilofar Bakhtiar who was supposed to have hugged her coach, a Frenchman, after completing a para-jump in France to gather funds for charity.