The advance could lead to tissue-transplant operations for a range of debilitating disorders, such as Parkinson's disease, multiple sclerosis, heart disease and spinal cord injuries.

Last year, a team created stem cells from the skin cells of babies, but it was unclear whether it would work in adults.

However, a team of scientists from the Research Institute for Stem Cell Research at CHA Health Systems in Los Angeles and the University of Seoul said they had achieved the same result with two men, one aged 35, the other the 75-year-old. "The proportion of diseases you can treat with lab-made tissue increases with age. So if you can't do this with adult cells it is of limited value," said Robert Lanza, co-author of the research, which was published in the journal Cell Stem Cell.

The technique works by removing the nucleus from an unfertilised egg and replacing it with the nucleus of a skin cell. An electric shock causes the cells to divide until they form a "blastocyst", a small ball of a few hundred cells.

In IVF, a blastocyst is implanted into the womb, but with the new technique the cells would be harvested to create other organs or tissues.

The breakthrough is likely to reignite the debate about the ethics of creating human embryos for medical purposes and the possible use of the same technique to produce cloned babies - which is illegal in Britain.

Although the embryos created may not produce a human clone even if implanted in a womb, the prospect is now closer. However, scientists have tried for years to clone monkeys and have yet to succeed.

Dr Lanza admitted that without strong regulations, the early embryos produced in therapeutic cloning "could also be used for human reproductive cloning, although this would be unsafe and grossly unethical". However, he said it was important for the future of regenerative medicine that research into therapeutic cloning should continue.

Shoukhrat Mitalipov, a reproductive biologist from Oregon Health and Science University, who developed the technique last year, said: "The advance here is showing that [nuclear transfer] looks like it will work with people of all ages.

"I'm happy to hear that our experiment was verified and shown to be genuine."

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Cloning advance means human tissues could be regrown, even in old age