Religious groups warned it could lead to preachers being prosecuted for emotionally expressing their firmly-held beliefs and will restrict freedom of speech.

They said gay rights were being given priority over Christian values and that believers felt under threat.

Ministers insisted any new law is aimed at extremists, and that people would not be prosecuted merely for expressing an opinion.

But sources admitted it would be up to police and the Crown Prosecution Service to decide whether charges should be brought in any individual case.

Colin Hart, director of The Christian Institute, said: "In a democratic society people must be free to express their beliefs without fear of censure from the state.

"A homophobic hatred law would be used by those with an axe to grind against Christians to silence them. People shouldn't face prison for expressing their sincerely-held religious beliefs."

An Institute spokesman added: "The criminal law will extend to the pulpit and we could have vicars standing before a court trying to defend themselves."

Massoud Shadjareh of the Islamic Human Rights Commission said: "If someone is reading the Bible and calls homosexuality an abomination, is that going to be incitement? There are similar passages in the Koran and the Talmud.

"I was against the incitement to religious hatred legislation. Either you water it down until it becomes pointless or you have a situation where you deprive people the right to have access to freedom of speech."

Mr Straw wants the new offence added to the Criminal Justice and Immigration Bill currently going through Parliament.

It will mirror the incitement to religious hatred law which carries a maximum penalty of seven years.

Richard Underwood of the Fellowship of Independent Evangelical Churches said: "I think Christians feel under threat here. Lots of Christians do not subscribe to the gay lifestyle but have a great heart.

"But gay rights always trump Christian rights, despite the fact this country based its laws on Christian rights for many hundreds of years."

The Ministry of Justice insisted a new law would not prohibit "criticism" of homosexuals. Gay and lesbian rights group Stonewall, which has been lobbying for such a law for several months, claimed it would not affect the right to express beliefs "in temperate terms".

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