John Ansell, the director of project development at the UK Stem Cell Foundation, said that the policy could lead to a brain drain of scientists and declining funding for Scottish research.

Following the ban imposed in 2001 by George Bush, who opposed the use of embryos for research, Scottish universities benefited from an influx of funding which helped make Scotland a world leader in the field.

The change in policy would have serious implications for the Scottish stem cell research industry. It had been estimated that the research could by worth at least £50m a year to the Scottish economy by 2015.

Scientists fear experts will be drawn to America by higher salaries and state-of-the-art facilities receiving federal funding.

Two small-scale medical trials are due to take place in Scotland this year; one in Glasgow to study the use of adult stem cells to treat stroke patients, the other in Edinburgh for the treatment of corneal blindness.

“If the trials turn out to be successful, lots of money will start rolling in,” added Ansell. “We still have an advantage, but it’s going to disappear, especially if America puts more money from the state into this.” The next trial in the pipeline in Scotland is the use of stem cells to repair damaged cartilage. Led by Dr Brendon Noble, of Edinburgh University’s centre for regenerative medicine, the trial is a collaboration with Geron, an American biotech firm.