LONDON - The British government on Wednesday approved plans to allow women to donate eggs for stem cell and cloning research -- and said they will also be entitled to compensation for costs incurred.

Women undergoing fertility treatment will receive a discount if they donate eggs, authorities said, while others will receive up to 250 pounds (about US$500) for each fertilization cycle to cover costs such as travel or lost work time.

The eggs would be used to create cloned embryos, with the hope of extracting stem cells. Because stem cells have the potential to become any cell in the body, scientists believe studying them could lead to cures for numerous diseases, including Parkinson's, Alzheimer's, or motor neurone diseases.

Some British stem cell experts are concerned that the change in policy -- which brings the country in line with several other European nations -- will encourage women to donate eggs solely for financial motives.

"It's exploitative because there will be women attracted even by the thought of getting 250 pounds from this," said Dr. Stephen Minger, director of the Stem Cell Laboratory at King's College. London. "I'm very uncomfortable with the idea of selling tissue and body parts."

Other experts accused authorities of downplaying the health risks to potential egg donors.

But the Human Fertilisation and Embryology Authority -- which advised the government -- stressed that payment would strictly cover expenses only.

"No one would be handing out money for donated eggs," said Gemma Wilkie, an HFEA spokeswoman. "We are only talking about recompense for costs incurred."

Britain has long permitted a practice known as egg-sharing, in which women get cheaper in-vitro fertilisation treatments for donating eggs to other women hoping to get pregnant -- but donated eggs could never before be used for research.

Some experts argued that women should be entitled to more than 250 pounds.

"Eggs are already a highly prized commodity," said Anna Smajdor, a medical ethics researcher at London's Imperial College. "250 pounds fails on all counts: it is enough to entice women from poorer countries while failing to represent the market value of eggs."