LONDON - Prime Minister Gordon Brown has been criticised by a number of leading religious leaders as he called on Sunday for members of parliament to offer their support for research using embryonic stem cells, which controversially includes human-animal hybrid embryos.

|PIC1|The Prime Minister has come under attack following his endorsement of the controversial Human Fertility and Embryology Bill. Cardinal Keith O'Brien, who has called work on human-animal embryos as a form of "Frankenstein Science", was united in his condemnation of Brown's comments along with the leaders of the Catholic Church in England and Northern Ireland.

The Times has also reported that 14 other Christian leaders from other denominations, have made a united appeal against parts of the bill, including the creation of so-called saviour siblings.

Brown's comments come ahead of an important vote in parliament on the issue scheduled on Monday.

The issue of embryonic cell research has divided the Labour government, and Christians as well as other faith groups have condemned the proposals saying that it is ethically wrong.

Cardinal O'Brien, Cardinal Cormac Murphy-O'Connor and Cardinal Sean Brady in a joint statement today said: "Not nearly enough time has been given to discussing these issues and these questions require answers before and not after legislation.

"We support scientific research that seeks to cure disease and suffering. The HFE Bill has focused on embryonic stem cell research.

"In fact, much greater progress has already been made towards clinical therapies using adult stem cells. Other emerging techniques hold potential for good, without creating and destroying human embryos."

In addition a letter signed by bishops, clergy and the heads of national Christian organisations said: "We would like to make it plain that as people from other Christian traditions we are completely opposed to the creation of animal-human hybrids, saviour siblings and the removal of the obligation on IVF clinics to consider the child's need for a father.

"This is not a narrowly Roman Catholic issue, nor is it a narrowly Christian issue nor indeed is it a narrowly religious issue. It is a human issue. We need to fight to uphold and protect our humanity."

At a time when Brown is not faring well in opinion polls, he has decided to allow a "free vote" in parliament on Monday on some of the most controversial parts of a human reproduction bill. Therefore, even though the prime minister has backed the bill, he is allowing members of his party to oppose them without being required to resign from the cabinet.

Brown has made his stance on the issue very clear, publicly declaring in the Observer newspaper that the research could "save and transform millions of lives" by providing important therapies to fight disease.

"That is why we have -- patiently and with full regard for religious concerns -- sought to introduce clear laws which permit the use of stem cells within a clear, managed, legal framework subject to the strictest supervision," Brown wrote.

British scientists have been pioneers in research on using "stem cells" -- undifferentiated cells that can turn into many types of tissue -- to cure disease.

Among the controversial aspects of the research are the so-called hybrid embryos, which involve putting human DNA into cells derived from animals to produce stem cells.

Brown wrote: "Around the world, researchers now face a severe shortage of embryonic stem cells. They argue that the safest way to maintain progress is to make use of animal eggs from which the animal genetic material is almost entirely removed, then a human cell nucleus added, to make them compatible for research on human diseases."

Brown is seen as strongly committed to stem cell research, an issue that affects him personally because his youngest son Fraser has the genetic disease cystic fibrosis, a condition that might one day benefit from stem cell-derived treatment.

Monday's debate is expected also to see heated discussion of abortion, with a number of MPs seeking to amend the bill to reduce the 24-week period in which women are normally permitted to terminate pregnancies.