The world's largest medical charity spoke to focus groups to gauge public opinion and found many people to have grave worries about a future society in which reproduction can occur without the need for men.

The survey found virtually no support for cloning for reproductive purposes, even in those groups which might have been expected to be sympathetic, such as infertile couples. One pregnant woman told the trust: "I was shocked to learn that babies can be conceived without a male being present."

The opposition expressed by the focus groups stemmed from concerns for the children and society as much as from fears about "unnatural" science.

The trust says it was also clear from the research that not only can the public understand the science, they are also able to grasp the ethical and social implications quickly.

New technology

Technology has moved very fast in the last few years. It was shown with Dolly the sheep that it is possible to clone a mammal by taking an adult cell, isolating its genetic material and implanting it into a nucleus-free egg that can then grow in a surrogate mother into a healthy foetus.

In the last few months, American researchers have managed to isolate and maintain human embryonic stem cells in the laboratory. These are the "master cells" for all the tissues in the body. If researchers can learn to control and direct their growth, it could be possible to grow specific tissues in the lab for use in transplant surgery.

Some scientists are even talking of combining the stem cell and cloning technologies as a means to produce tissues and even whole organs that would not be rejected by the body as foreign.

Initially, the trust says, people were prepared to support the idea of cloning technology to create stem cells which can be grown in the lab. But later, having thought about the implications of the technology, they expressed growing concern at the idea of using a potential "twin" as a source of spare parts.

One person told the trust: "It could be psychologically disastrous if you created an embryo to create a part for yourself and then destroyed it."

Ordinary people

Dr Suzanne King, head of the trust's Consultation and Education Department, said the charity wanted to put the views of ordinary people into the debate about cloning.

"We went out and explored in depth with people what they meant by cloning and what they thought it was. Then we explained some of the science to them and got their considered opinion.

"We used very simple diagrams to explain how you would clone a human being and produce a baby."