Government plans to keep the ancient blasphemy law while outlawing incitement to racial hatred have been criticised in some quarters.
John William Gott got hard labour for 'blaspheming' Christianity
Critics had hoped a repeal of law - which solely applies to criticising the Church of England - would be announced in the Queen's Speech last week.
But Home Office minister Fiona Mactaggart told the BBC there were no plans to repeal the law.
Lib Dem MP Evan Harris said free discussion of religions was at risk.
He said by keeping the blasphemy law the government was sending out the wrong message to people of other religions - suggesting that restricting free speech was acceptable.
Dr Harris told BBC Radio 4's Today programme: "There is a great deal of worry that such a law will prevent, either directly or indirectly through self-censorship, legitimate criticism of religion, which - given the world we face at the moment - is absolutely critical."
Repealing the blasphemy law would "send a signal" that the new legislation is designed to prevent the incitement of hatred and not to stifle debate, he said.
"People of religious views are sensitive and do take offence, but in a free society, we need to ensure that people are free to criticise religions and criticise each others religions," said Dr Harris.
"The government claims that this law is not about restricting the ability to criticise religion, but one key marker of whether we can believe that is whether they abolish the discriminatory law of blasphemy, which specifically protects Christian belief and doctrine from attack.
"The problem is that there is a number of, for example, Muslim commentators who feel that the law the government is bringing in will give them equality with
Christianity [over blasphemy].
"If that isn't the case, the government needs to repeal to show that the law they are bringing in is not about restricting the ability of people in a free society to criticise ideas, even if that is offensive."
In a statement, the Home Office told the BBC: "The priority is to fill the gap in criminal law so that people of all faiths are protected against incitement to religious hatred.
"It is going to be taken forward in the Serious Organised Crime and Police Bill. The Home Office will continue to keep blasphemy laws under review but at the moment we have no plans for repeal."
There have been no public prosecutions for blasphemy since 1922 when John William Gott was sentenced to nine months' hard labour for comparing Jesus with a circus clown
The only successful private prosecution since then was the case brought by Mary Whitehouse in 1977 against Gay News over a poem it printed depicting Christ as a promiscuous homosexual.