Roman Catholic bishops in Scotland have criticised plans to allow mixed human-animal embryos for stem cell research, and on Thursday made an urgent call for MPs to reject the proposals.

Last week the UK Human Fertilisation and Embryology Authority (HFEA) agreed to the principles of allowing scientists to create hybrid embryos - a move described as a "horrific prospect" by Scotland's Catholic bishops.

The Church is saying that a "moral boundary is being crossed" by the proposals, which involve removing nuclei from animal eggs and replacing them with DNA from human cells.

However, the HFEA have agreed that the move could lead to developments in therapy for diseases such as Alzheimer's and Parkinson's.

MPs have been called on by the Church to reject "such controversial and morally questionable techniques".

The Catholic bishops added that research with "non-controversial adult stem cell therapies have produced many successes", and that the current proposals are unnecessary and immoral.

The Church said in a statement: "Human beings are unique and distinct from all other creatures.

"Our natural distaste at the prospect of mixing species reflects a natural intuition that a moral boundary is being crossed. We are appalled and shocked by this horrific prospect."

It concluded: "It is alarming to imagine a new category of embryo being fashioned by scientists in order that they might have a further supply of raw genetic material on which to experiment and discard. Creating hybrids between animals and humans would be a step too far."