Researchers in the US working with human embryonic stem cells might move abroad or abandon their research if an injunction on the federal funding of their research is not overturned, the director of the National Institutes of Health has warned.

A district court in Washington DC granted the injunction after deciding that a lawsuit against the NIH was likely to succeed because the institutes' policy on funding such research violated a ban on federal funding for work involving the destruction of human embryos.

The plaintiffs, James Sherley of the Boston Biomedical Research Institute and Theresa Deisher of biotech firm AVM Biotechnology, also argue that embryonic stem-cell research takes funding from researchers like themselves, who work with adult stem cells.

Their lawyer confirmed that the two plaintiffs are ethically opposed to embryonic stem-cell research but said their suit was "based on the NIH's violation of federal law". The injunction appears to apply even to the small number of projects approved for federal funding by the George W. Bush administration.

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The Obama administration, which overturned Mr Bush's restrictions on embryonic stem-cell research last year, has confirmed that it will appeal against the injunction.

Francis Collins, NIH director, said he was "stunned" by the injunction, which "has the potential to do serious damage to one of the most promising areas of biomedical research just at a time we were really gaining momentum".

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He said the injunction did not apply to grants that had already been allocated, but 22 grants due for annual renewal by the end of this month would be hit, as would another 150 due for renewal in the next year.

More than 60 submitted applications also had to be mothballed, he said.

"Researchers who were so energised by the opportunities made available over the last year will likely get discouraged and maybe move to other countries or other areas of research. We will lose momentum," he said.

Sean Morrison, director of the Center for Stem Cell Biology at the University of Michigan, said the injunction would do "greater harm to ESC researchers than any policy ever enacted".

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paul.jump@tsleducation.com.