In an attempt to regulate such developments, the UK Government has announced new guidelines covering human-to-animal transplants or the use of animal organs by humans.

Transplant trials ready to go ahead

Many scientists have experimented with transplanting animal organs in a process known as 'xenotransplantation'.

None, however, has succeeded in overcoming the problem of the organ being rejected by the patient's body.

The BBC's Fergus Walsh: First trials could happen abroad

Researchers at Imutran, a company based in Cambridge, England, believe they have found a way round this by slightly altering a pig's genetic make-up. This "fools" the body into accepting the organ.

However, the pig's liver will not be transplanted into the patient's body. It will remain external, like a kidney dialysis machine.

Disease fears

The BBC's Richard Hannaford: 'It's ready to go'

Although some scientists think that allowing humans to use pig organs could enable an as yet unknown but potentially lethal disease to jump the species barrier, Imutran says it has no evidence to support this theory.

Imutran is thought to be preparing an application to the government committee which regulates this area of science, asking for permission to carry out the first operation to allow humans to use animal organs.

This would use the genetically-altered organs.

Dr Corin Saville of Imutran and Professor Robert Weiss of the Institute of Cancer Research, discuss the issues

On Thursday, the Health Secretary Frank Dobson announced further regulations on transplantation and human use of animal organs, enabling the committee to deal with any such submissions.