Gordon Brown executed an embarrassing U-turn yesterday as he ceded to pressure from the Roman Catholic Church to offer Labour MPs free votes on legal changes for embryo and fertility research.

Faced with increasing attacks from Catholic bishops, threats of resignation from several ministers and taunts from David Cameron, he announced that ministers and backbenchers could vote against the three most controversial measures.

The free votes will apply to the creation of human admixed embryos containing both human and animal material, for studying serious diseases. They will also cover “saviour siblings”, which are screened as embryos to ensure their suitability to donate umbilical cord cells to sick children.

The third unwhipped vote will decide on removing the requirement that IVF clinics consider a child’s need for a father, to give full rights to single women and lesbians.

In an admission that the proposals have been poorly handled, Mr Brown will now lead a push to explain their purpose and the benefits at stake before the legislation comes to the Commons.

But his plans to raise awareness of the changes to the framework for research and fertility treatment using human embryos got off to a poor start after a slip by Mr Brown in announcing the areas to be subject to free Commons votes.

He referred to one of these as “IVF research”, forcing embarrassed officials to admit he meant the removal of the legal duty to consider a child’s need for a father when permitting in-vitro fertilisation treatment. Sources said that he should have referred to “IVF treatment”.

While scientists were broadly supportive of the free votes, several said privately that they were disappointed that Mr Brown had spread further confusion about the Bill.

“It is most unfortunate that the Prime Minister seems to have confused the ‘need for a father’ clause with IVF research, which has nothing to do with it,” one said.

Signs of tension also emerged within the Government over the issue, with sources close to Alan Johnson, the Health Secretary, who is in charge of the legislation, blaming Geoff Hoon, the government Chief Whip, for the delay in offering free votes.

Mr Brown will still require Labour MPs to vote for the Human Fertilisation and Embryology Bill at its second reading, due in May, and its third reading, after the controversial elements are settled on free votes.

But supporters and critics agreed that Mr Brown’s announcement drew heat from the row and would split its opponents in the Commons. A minority will oppose it throughout, others will abstain on other votes while a further group, including up to ten ministers, are expected to vote against some provisions but later back the Bill, ensuring that it will pass into law.

Evan Harris, the Liberal Democrat MP and supporter of the Bill, said that analysis of past votes suggested that up to 50 Labour MPs may vote against some provisions but would be offset by 40 Tories and 50 Lib Dems voting in favour, which should ensure clear majorities. However, the Government will whip a separate vote allowing two women to register as parents on a child’s birth certificate.

Jim Dobbin, the Labour MP and chairman of the all-party Pro-Life Group, is among those who will oppose the Bill at second reading. But he said: “Essentially, it is welcome news. Why the Government did not do this in the first place, I will never know.”

After a weekend of outspoken attacks on the measures, church leaders also struck a more soothing tone in welcoming Mr Brown’s change of tack although they signalled that they would continue to argue against the Bill.

The Catholic Archbishop of Westminster, Cardinal Cormac Murphy-O’Connor, said in a joint statement with the bishops’ conference: “The free vote will be welcomed by people of all faiths or none who are concerned about the implications of this Bill that go to the heart of what it means to be human.”

Medical research leaders and patient groups also applauded the decision, saying they hoped it would allow debate to focus on the medical potential of research, not parliamentary procedure.

Professor Robin Lovell-Badge, of the National Institute for Medical Research, said: “I am not against a free vote, as long as the MPs understand what is being proposed in the Bill and why.”

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