Governments across Europe must do more to safeguard freedom of speech for Muslim reformers who face threats from extremists, a think tank has warned.
The UK-based Centre for Social Cohesion highlighted the cases of 27 writers, including Sir Salman Rushdie, activists, politicians and artists.
The centre said they had suffered violence and intimidation for criticising Islam or seeking reform.
It said governments had a duty to ensure free speech for all citizens.
The report - Victims of Intimidation: Freedom of Speech within Europe's Muslim Communities - said official failure to offer victims the protection they needed had left "significant numbers" of Muslims unable to express themselves.
It said this also created the impression that more Muslims were opposed to free speech than was actually the case.
The centre called for European governments to "promote greater religious and social harmony by demonstrating that they see Muslims and those of Muslim background as complete citizens, neither restricted in their freedoms nor unduly permitted to issue threats against others".
Sir Salman was among the cases highlighted.
The Booker Prize-winner lived in hiding for nine years after Iran's late Ayatollah Khomeini imposed a fatwa, or death threat, on him in 1989 after the publication of his novel The Satanic Verses.
The ayatollah said the book was "blasphemous to Islam".
The report also considered the case of Maryam Namazie, who received threats after setting up the Council of Ex-Muslims in Britain, and Cardiff-based humanist writer Anwar Shaikh, the subject of a fatwa demanding his hanging.
It also featured the case of pop singer Deepika "Deeyah" Thathaal, a Norwegian pop star of Afghan and Pakistini origin, who said she had been threatened, spat at and attacked with pepper spray after a video showed her removing a burka, the Islamic veil, to reveal a bikini.
And Syrian-born Danish MP Naser Khader, who founded the organisation Democratic Muslims in the wake of the Prophet Muhammad cartoon row, lives under 24-hour police protection, said the think tank's report.
Reform
Douglas Murray, director of the Centre for Social Cohesion and co-author of the report, said Muslims found it increasingly difficult" to criticise elements of their faith or culture without fear of reprisal.
In a free society, no belief or set of values should remain beyond open criticism," he said.
To grant a belief system amnesty from discussion concedes that intimidation and violence can succeed.
Unless Muslims are allowed to discuss their religion without fear of attack there can be no chance of reform or genuine freedom of conscience within Islam."
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