A bill to criminalise offences against "sacred values," filed in parliament this week by Tunisia's ruling Islamist party Ennahda threatens freedom of expression, Human Rights Watch warned on Friday.
"The draft bill would provide prison terms and fines for broadly worded offenses such as insulting or mocking the 'sanctity of religion,'" the rights group said.
International human rights law generally prohibits criminalising the defamation of religion, the New York-based watchdog added.
"If passed, this draft law would introduce a new form of censorship in a country that suffered from so much censorship under the ousted president," Zine El Abidine Ben Ali, HRW deputy regional director Eric Goldstein said.
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The bill, filed in the National Constituent Assembly on Wednesday, could hand a prison sentence of up to two years to anyone convicted of violating sacred values and up to four years for repeat offences.
It lists subjects held sacred in the three Abrahamic religions, including God and the Prophet Mohammed, the earlier prophets, the holy books, mosques, churches and synagogues.
It also codifies the levels of offence to religious feeling, including "insults, profanity, derision and representation of Allah and Mohammed," something prohibited in Islam.
Ennahda, at its first congress on home soil in 24 years, indicated last month that it planned to introduce such legislation, after an art exhibition that some deemed offensive to Islam sparked riots in Tunis and elsewhere.
It is not clear when the bill will come up for debate, but it is likely to be a stormy session, with the government having already been strongly criticised over the sensitive issue.