The leader of the Roman Catholic Church in England and Wales has begun an unprecedented attempt to block new laws on embryo research by contacting all Catholic MPs in a personal lobbying campaign.

The Archbishop of Westminster, Cardinal Cormac Murphy-O’Connor, has invited them to a reception next week to discuss in confidence “issues likely to come before the House in the new session of Parliament”.

MPs say that the move signals a shift towards a more outspoken political role for the Church.

They told The Times that the event was the first of its kind and clearly triggered by the current legislation on fertility treatment and embryo research and by further debates on abortion law, which are expected next year.

While the Catholic Church in Scotland has traditionally enjoyed a high profile in political life, its counterpart in England has generally been more reticent.

Ministers are preparing for a parliamentary battle over the Human Fertilisation and Embryology Bill, which government sources toldThe Timeswould be whipped strongly to prevent its opponents from forcing through wrecking amendments.

Such tactics present a dilemma for Roman Catholic Labour MPs, including Ruth Kelly, the Transport Secretary, who as a backbencher opposed regulations on stem-cell research. She has refused to say whether she will vote for the Bill. But senior ministers told The Times that there was no prospect of Ms Kelly and other Roman Catholic Labour MPs being given a free vote on the proposals. “This is a government Bill and Ruth will have to vote for it if she wishes to stay in the Government,” said one figure.

There are 68 MPs who describe themselves as Roman Catholic, according to The Catholic Register, although its list includes three Sinn Fein MPs who refuse to take the Commons oath and the Speaker, Michael Martin, who does not vote. This makes the number of voting Catholic MPs 64, including several from minority parties.

Previous recent interventions by the Roman Catholic Church, such as to block restrictions on admissions to church schools and oppose provisions allowing gay couples to adopt, were seen as clumsy, leaving some MPs complaining of a lack of warning or consultation by the Church. David Amess, a Tory MP and chairman of the all-party group on the Holy See, said: “I think it is a very good thing. Having been in Parliament when we have had these debates before, on occasions some colleagues have felt very disappointed that, for instance, Church leaders – and that includes the Catholic Church – have not been more vociferous.”

The Archbishop of Birmingham yesterday described the situation where same-sex partners registered themselves as the legal parents of a child as the creation of a “fictional parenthood”.

In a speech at the annual Civic Mass in St Chad’s Cathedral, Birmingham, The Most Reverend Vincent Nichols said: “Can it be wise, or even acceptable, that the law may no longer require a record of the true parents to whom a child is born, permitting instead two people of the same sex to register as the parents of the child from birth?”

He added that telling a child that they do not have a biological father was “the ultimate act of spin”.

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