Churches have expressed their regret after researchers at the University of Newcastle announced this week that they had created human-animal hybrid embryos.

University of Newcastle researcher Lyle Armstrong was given the green light to create the embryos by the Human Fertilisation and Embryology Authority in January, in a move that angered Catholics.

The Catholic Bishops' Conference of England and Wales said in a statement on Wednesday, "It does seem extraordinary that the HFEA should have granted a license before there has been a full public and parliamentary debate.

"There must be a thorough public discussion about the serious ethical issues raised by the possibility of creating human-animal hybrid embryos."

The Church of Scotland said in a statement on Wednesday, meanwhile, that it "regrets" the creation of the "admixed embryos", which were generated by removing the nucleus of a cow egg and replacing it with human DNA.

In its 2006 and 2007 General Assemblies, the Church of Scotland stressed its opposition to the creation of animal-human embryos and instead urged the Government to encourage research into stem cells derived from adult tissues and placental cord blood, and to work to find therapeutic solutions which avoid embryo use.

The Church of Scotland also previously stated that the creation of human-animal hybrids is a "line which should not be crossed". In light of their creation by the University of Newcastle, the Church added, "That this line appears to have been traversed is a matter of grave concern to the Church."

John Burn, head of the Institute of Human Genetics at Newcastle University, defended the creation of the hybrid embryos, saying in a statement that they would "open the door to a better understanding of disease processes without having to use precious human eggs".

Last month, the head of the Catholic Church in Scotland, Cardinal Keith O'Brien, faced fierce criticism after he likened research into the creation of hybrid embryos to "experiments of Frankenstein proportion".

In his Easter sermon, the Cardinal also denounced the Human Embryology and Fertilisation Bill as a "monstrous attack on human rights, human dignity and human life". According to a survey of 1,005 people conducted for the Catholic Church in Scotland, two-thirds of voters support the Cardinal's position.

The Church of Scotland added that it was "especially regrettable" that the Bill, currently passing through Parliament, would enshrine research into human-animal embryos in the law books.

The Church also expressed its "unease" over what it believes is the misrepresentation of the debate over embryos as one of "scientists versus the church".

"This false dichotomy, and the emotive terms sometimes deployed, are to be regretted," it said.

Supporters claim that denying such experiments would delay cures for terminal illnesses. The Church dismissed such claims, however, as "irresponsible and unjustified".

It concluded, "The Church welcomes vigorous and informed debate, and reiterates its view that all scientific endeavour must be properly ethically informed."