Hundreds of Christians have protested outside Parliament against a proposed law which would ban incitement to religious hatred.
Opponents say the law will damage freedom of speech
The demonstration by a coalition of groups was timed to coincide with the second reading of the Racial and Religious Hatred Bill in the Lords.
Opponents say it will damage freedom of speech and worsen community relations.
But Home Secretary Charles Clarke says it will only affect "extreme behaviour" and not prevent poking fun at religion.
The Reverend Katei Kirby, African and Caribbean Evangelical Alliance chief executive, said: "It affects everyone so deeply.
"This is not just about doctrine. This is not even about theological opposition. This is about our basic freedom to speak and to preach.
"It affects people's freedom to discuss and to critique anything because it might upset or offend somebody else and that is very serious."
The National Secular Society also took part in the demonstration.
Vice-president Terry Sanderson said: "We are coming at it from a completely different angle from the Christians.
"They are looking at the restrictions on their right to evangelise. We are looking at the restrictions on our being about to criticise religion per se so we can make common cause with them on this.
"I think this is an indicator to the government of just how wide the opposition is."
Mr Clarke recently said he wanted to stop "nasty and extreme behaviour" which destroyed individuals and divided communities.
Similar measures proposed by the government have faced much opposition and failed to make it through Parliament.
One of the most prominent campaigners against the planned law has been Blackadder actor Rowan Atkinson.
About 300 people took part in a demonstration against the Bill in London's Hyde Park on Saturday.