Gordon Brown said today that Labour MPs could vote with their consciences on three sensitive elements of his controversial embryo research plans, in an attempt to stave off a potential rebellion.

The Prime Minister continued to refuse MPs a free vote on the Human Fertilisation and Embryology Bill, saying that they would have to vote with the Government when it has its second and third readings in the House of Commons.

However – amid concern that the Government faced a significant revolt from Roman Catholic MPs – Mr Brown pledged a free vote when individual sections, or amendments, of the Bill are cherry-picked and debated between the two readings.

MPs would be allowed to vote with their consciences on amendments dealing with three particularly sensitive areas, those dealing with IVF research, saviour siblings and mixing embryos, he said.

Mr Brown added that he would continue to urge MPs to support the legislation in its entirity, saying that he was writing to every MP in the party to explain why he backed it.

Today's move comes after a weekend of agonising by the Prime Minister amid fears that three Catholic Cabinet ministers, Ruth Kelly, Des Browne and Paul Murphy, and backbench MPs could vote against the Government.

The Catholic Church this afternoon said that Mr Brown's acknowledgement of MPs' consciences was "better late than never" but added that the Bill still contained some "deeply troubling proposals".

In addition, at least one Catholic Labour MP said she would still rebel throughout the Bill's House of Commons stages unless aspects of the legislation are changed.

Scientists welcomed the decision to give MPs a free vote, saying that they hoped that it would end the politicisation of a scientific discussion.

Dr Stephen Minger, Director of the Stem Cell Biology Laboratory at King’s College London, and one of the scientists who hopes to carry out research using the "admixed" embryos, said: "I think one thing we have proved over the past year is that the scientists who want to do research on human admixed embryos are prepared to spend huge amounts of our time explaining to the public and policy makers why we want to do this and exactly what is involved.

"I welcome any opportunity to debate this further and I hope that Gordon Brown’s announcement today will put an end to the political point scoring and move the debate back to the science and ethics of this research."

Professor Colin Blakemore, former head of the Medical Research Council, said: "I hope that this decision to allow a free vote will take some of the heat out of this issue. However, this makes it even more important that MPs should be fully and accurately informed about the science underpinning the Bill.

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