David Cameron issued a note of caution yesterday to critics of embryo research and predicted that Gordon Brown would be forced to offer a free vote to Labour backbenchers on government plans.

The Conservative leader said that voters would think the Prime Minister had “lost his way” if he forced Labour MPs to support him on an issue that many regarded as one of conscience.

Mr Cameron, whose eldest child Ivan has the neurological condition Ohtahara syndrome and is severely disabled, sounded a cautionary note to the Roman Catholic Church and other critics, saying that they must not misrepresent the proposals.

His intervention came as scientists prepared to meet Catholic MPs and Church leaders concerned about the legislation to explain why they wished to conduct experiments with human-animal embryos, which the Bill would permit for the first time.

After a letter in The Times yesterday, in which Professor Colin Blakemore, the former head of the Medical Research Council, proposed such a dialogue, the Labour MP Jim Devine approached stem-cell scientists offering to arrange such a meeting. Mr Devine, a Catholic, has led opposition to attacks on legislation and branded “completely unacceptable” comments by Cardinal Keith O’Brien, Scotland’s most senior Catholic, who said that it was a “monstrous attack” on human dignity and life that would allow experiments of “Frankenstein proportion”.

Stephen Minger, director of stem-cell biology at King’s College London, said: “The purpose of this meeting will be to clarify a number of scientific aspects of the fertility Bill, and in particular why scientists need to pursue research using human admixed embryos. We have proved over the past year that we are more than happy to engage with the public and policy-makers on these issues but we are concerned that society is allowed to have this important debate on the basis of good, accurate information.”

Mr Cameron said that the Catholic Church was entitled to express its opinion, but added: “There is a danger that people can overstate what is in this Bill and that is all the greater need for it to be debated calmly and reasonably in Parliament. My own view, and I think [that of] many people in the Conservative Party, is we need to update the legislation. This sort of research is important. We all want to see diseases reduced and problems that children have, birth defects, dealt with.”

In a reference to his son’s condition, Mr Cameron told Sky TV: “Anyone with children who suffer these sorts of conditions knows how important this work is. But we shouldn’t be frightened of having a frank and realistic debate about it in Parliament. If anyone misleads anyone about this Bill then clearly that’s wrong.”

A Church of England bishop became the latest religious leader to speak out against the Human Fertilisation and Embryology Bill.

The Bishop of Lichfield, the Right Rev Jonathan Gledhill, said: “It’s a very important part of our society and a very important part of the Christian faith that you should have respect for human embryos. If you stop obeying God, you start to limit the rights of human beings and this is a case in point. A society has to be judged by the way that it treats its poorest, most vulnerable and weakest. And what can be weaker than an unborn child?”

The Prime Minister has hinted at a compromise, saying that every MP should have the right to exercise their conscience, but has left unclear whether ministers and backbenchers will be offered a deal under which they can absent themselves from the Commons rather than vote for the measures, or be allowed a free vote that would allow them to vote against.

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