Will Cabinet Catholics put career before conscience on embryo research?

Ruth Kelly, Des Browne and Paul Murphy should actively oppose the legislation and put their consciences before their Cabinet careers, say campaigners.

In total, 18 members of the Government, including the Cabinet trio, are understood to be unhappy about measures in the Human Fertilisation and Embryology Bill, including the creation of hybrid animal-human embryos.

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Chief Whip Geoff Hoon has announced he will allow ministers to abstain from the Commons votes - but has warned they must not vote against the Bill if they want to remain in Government.

Transport Secretary Miss Kelly, Defence Secretary Mr Browne and Wales Secretary Mr Murphy have not publicly declared how they plan to vote when the laws are put to MPs in the next few weeks.

They would be forced to resign if they defied the Government whip and are pressing for a free vote.

There is no date set for the second reading of the Bill because of the growing row.

It cleared the House of Lords last month but it is unlikely there will be a vote before the middle of April.

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But Catholic backbench Labour MPs have dismissed the offer of abstaining and vowed to vote against, putting pressure on ministers.

The Bill contains controversial measures to allow mixing of human and animal embryos to create hybrids for scientific research into fatal diseases. The hybrids would then be discarded.

It would also allow lesbian couples to register as joint legal parents of a child born through fertility treatment, removing the need for a father.

Culture Secretary Andy Burnham is Catholic but is not planning to block the laws. Other Catholic Ministers include Pat McFadden, David Cairns and Mike O'Brien.

Greg Pope, Labour MP for Hyndburn, said: "I have had hundreds of letters from constituents about human-animal hybrids.

"The idea that I turn round to them and say the Chief Whip has given me the day off from voting will cut no ice at all."

David Cameron has given his MPs a free vote on the entire Bill.

But because the proposals are part of Government legislation, all ministers and Labour MPs will be subject to a three-line whip.

It is expected, however, that voting on the most contentious parts could be relaxed to a two line whip, to allow MPs with strong feelings to abstain.

The Bill will also trigger the first major Parliamentary vote on abortion in nearly 20 years.

A powerful alliance of pro-life and religious groups is planning to target individual MPs who refuse to back moves to reduce the legal time limit for terminations.

MPs are to face an unprecedented U.S.-style campaign designed to make their views on abortion a crucial issue at the next election.

It will be the first time many MPs will have had to make a choice one way or another on the issue. The last vote was in 1990.

Figures show the number of late abortions has soared.

In 2006, almost 3,000 terminations were carried out on women who were at least 20 weeks pregnant - a 44 per cent increase since 1997.

The vast majority were for "lifestyle" reasons, with less than a quarter because of a risk that the child would be born handicapped.

Amendments are being tabled to the Bill to bring the current 24-week deadline for abortion down to 20 weeks.

Pro-life MPs from all three main parties say a reduction is necessary because medical advances mean babies born before 24 weeks have a reasonable chance of surviving.

They also want to introduce a week-long period of "informed consent", during which women wanting a termination would be advised to reflect on their decision.

Today the Alive and Kicking campaign group - an umbrella organisation which includes the Christian Medical Fellowship, ProLife Alliance, the Guild of Catholic Doctors, the Evangelical Alliance, and the Lawyers' Christian Fellowship - will launch a campaign focusing on individual MPs.

Their views, previous voting records and how they go on to vote will be publicised on a website, www.aliveandkickingcampaign.org, which goes live today.

It also highlights MPs' Parliamentary majorities to indicate where pro-life voters might be able to influence the result at the next election.

A source at the campaign said: "Members of the public will for the first time be able to look and see what their MP's views are and how they have voted.

"They can then bring pressure to bear. The aim is to make MPs' individual voting records an issue, just as it is for American politicians."

Mr Cameron last month indicated his support for the legal time limit for abortion to be reduced by up to a month.

Dr Peter Saunders, general secretary of the Christian Medical Fellowship, said: "This is not a party political campaign - it's about one issue which polls suggest is an important one for a lot of people."