A senior Midland bishop last night condemned as immoral Government proposals which would allow the creation of hybrid human-animal embryos.

The Bishop of Lichfield, the Rt Rev Jonathan Gledhill, also joined other Anglican and Catholic Church leaders in calling on the Prime Minister to allow Labour MPs to have a free vote on the controversial legislation. The Government was said last night to be looking for a compromise which would allow MPs to abstain on certain parts of the Human Fertilisation and Embryology Bill so long as it does not threaten its passage through the Commons.

The move is believed to have been drawn up to stave off the potential resignation of three Cabinet ministers who are Catholic.

The Bishop of Birmingham the Rt Rev David Urquhart and the city's Catholic leader Archbishop Vincent Nichols have called for Labour MPs to be allowed a free vote.

Bishop Gledhill said he also wanted to see MPs allowed to follow their conscience, but he went further by attacking the research proposals.

He said: "Embryos are potential human beings and if we use them for experiments we are obviously mistreating them.

"If we stop obeying God, often the first casualty is humanity. We have a duty to protect the innocent and vulnerable, and the unborn are most definitely innocent and vulnerable."

The bishop also called for the Government to take more account of public opinion, saying: "We need to hear from ethics committees that have been set up, we need to hear whether it's something that the public would find acceptable, we need to see why exactly they want to carry out these experiments. I think most people are confused.

"It may be that if people have a horror of creating human-animal hybrids, they can reassure us." He gave his backing to calls from the Catholic Church to give MPs a free rein and let them vote based on their conscience.

Archbishop Nichols, the head of the Catholic Church in Birmingham, planned to use today's Easter Monday homily to put pressure on the Government to allow a free vote.

He was due to say: "We hear consistently the claims that the type of embryo experimentation being permitted by the Bill holds great promise for future cures of illness like cystic fibrosis and multiple sclerosis.

"The evidence is so far sparse. Very little progress has been made through embryonic stem cell research. In contrast, work with adult stem cells is showing far better results. The published research points in this direction, even in the task of finding cures for cystic fibrosis. Yet we hear little about it. What is to be lost in facing these facts? They indicate the pathways of successful research to which there are no ethical objections."

He will urge the congregation to write to their MPs demanding a free vote. A suggestion that dissenting MPs would be allowed to abstain if it did not stop the Bill "would not be good enough" and the archbishop said this would be a sign that there was no space for ethical objections in the Government.

Archbishop Nichols was also backed by his Anglican counterpart in Birmingham. Bishop Urquhart said: "I fully back the views expressed by the Catholic Church leaders. The Church's role in this debate is to provide moral insight."

The Human Fertilisation and Embryology Bill was drawn up to update legislation on the use of embryos in scientific research and therapy, as well as the rules governing IVF.

It will regulate the use of embryos, ban couples from selecting the sex of their baby except for health reasons, and allow "inter-species" embryos created from human and animal genetic material. If passed, the Bill will also make it easier for lesbian couples to have children using IVF, making it possible to name same-sex couples as the legal parents of a child.