Cord-blood transplants have tended to be used only on children as it was not thought to contain enough stem cells to rebuild the blood system in adults.

But the study showed the survival rate for cord-blood transplants was the same as for slight mismatched bone marrow - the second best alternative treatment.

The study examined 500 patients, the New England Journal of Medicine said.

Researchers analysed the treatment of leukaemia patients aged 16 to 60 years old.

The best survival rate, 33%, was for patients who had transplants from matched, unrelated donors.

Both cord blood and the mismatched bone marrow transplants from unrelated donors had a 22% survival rate, reported the study by the International Bone Marrow Transplant Registry, University Hospitals of Cleveland and New York Blood Center National Cord Blood Program.

More than 6,000 people are diagnosed with leukaemia in the UK alone each year.

Lead researcher Dr Mary Laughlin said the findings offered hope to those patients who cannot find a bone marrow transplant match.

"Umbilical cords that are normally discarded after birth could provide real hope for these patients," she said.

'Offers hope'

She said only one in five leukaemia patients can have bone marrow transplants from siblings, meaning most are forced to try to find a match from bone marrow donor lists.

"Only a small percentage of patients are lucky enough to find a transplant match at a registry, which is why cord-blood transplant is so important."

Dr David Grant, scientific director of the Leukaemia Research Fund, welcomed the study.

"It is certainly very interesting and offers hope to patients," he said.

"In the past doctors have shied away from cord-blood transplant on adults as it was not thought to contain enough stem cells."

However, he warned one problem with cord blood was that it could only be collected under stringent conditions.

There is only one cord blood bank in England.