Ken Macdonald told MPs that he wanted to play down Muslim expectations to avoid a backlash against police and politicians because very few cases were likely to reach the courts.

People will remain “perfectly free to be rude or offensive” about Islam or any other other religion because in most cases the right of free speech will still prevail, Mr Macdonald said.

He added: “It is very important people understand what the law will achieve. It will stop the grossest form of conduct but it will not stop people being rude about Islam.”

Mr Macdonald was speaking at the Home Affairs Select Committee, where he also repeated his caution to ministers to keep the right to jury trial even for terrorist suspects. He told MPs of his concern that religious incitement laws, part of the Serious Organised Crime and Police Bill, were expected by some to stop all forms of criticism or abuse of Islam.

The proposals have also been criticised for threatening to stifle free speech. Mr Macdonald said that they would not have been possible in the United States because of the First Amendment. But in the light of existing laws on incitement to racial hatred, British courts would “set the bar very high” before convicting, he added.

Since 2001 there had been 86 referrals to the Crown Prosecution Service for racial hatred but only six prosecutions and two convictions, with one dropped and three ongoing.

Mr Macdonald added: “The main issue is managing expectations . . . Communities have said they believe it will protect them from people being rude or offensive about Islam — but you are perfectly free to be rude or offensive about any religion and the law protects you.

“The danger is that if people believe it is going to protect them from that, they will feel very let down by us.”

He added: “The police will send us the files and we will see whether prosecution will meet the appropriate tests and if it does we will prosecute . . . But you will have to meet the very high level [of proof] required.”

The Muslim Council of Britain said that it shared Mr Macdonald’s concern to explain the law carefully.

Inayat Bunglawala, a council spokesman, said: “Not just Muslims fail to understand but also the likes of Rowan Atkinson, who has said it would prevent jokes and satire. So it has been misunderstood by those who want the legislation and those who oppose it.”