Hailing the field as "one of the most exciting and promising" in modern biomedical research, the group said they feared research grants currently under review may be under threat from pro-life European parliamentarians who say public funds should not be spent on embryonic stem cell work.

"(EU) Commission funding must be available to continue to support scientists investigating all types of stem cells - including human embryonic stem cells - with potential to make advances in regenerative medicine," they wrote in an open letter released by the Wellcome Trust, a charitable health foundation.

The European Parliament is currently debating the future outline of Horizon 2020, the EU's program for research and innovation which will run from 2014 to 2020.

Draft rules provide for stem cell research funding, including embryonic stem cells but some member states have been lobbying for embryonic stem cell research to be excluded.

Many scientists believe stem cell research has the potential to lead to the development of treatments for a whole host of diseases including incurable neurodegenerative illnesses such as Parkinson's, motor neurone disease and multiple sclerosis, as well as type 1 diabetes, various serious heart conditions, liver damage, spinal cord damage and blindness.

Europe, and particularly Britain, is considered a world leader in stem cell research. The experts, from charities, funding bodies and patient groups, said if Europe is to hold on to this competitive edge, it is crucial to maintain funding for all stem cell research.

Three main types of stem cells are currently used in research - adult induced pluripotent, embryonic and fetal stem cells. Embryonic stem cells are controversial because they are harvested embryos that a just a few days old.

Experts say it is too early yet to determine which route will be the most effective for developing effective treatments that can be used in patients in the future.

"This field of research is complex. To enable scientists to best understand the massive potential of stem cells, scientists must be able to continue research in all avenues," the open letter said.

"Any move to make human embryonic stem cell research ineligible for Horizon 2020 funding would risk holding back progress across the entire field.

Europe's first clinical trial using human embryonic stem (hES) cells has started in Britain, after being approved by regulators in 2011. Researchers are testing an experimental stem-cell-based treatment for Stargardt's disease - a progressive form of blindness.

The letter was signed by Association of Medical Research Charities, the British Heart Foundation, the European Genetic Alliances' Network, Britain's Medical Research Council, the charity Parkinson's UK and Wellcome Trust.

The Wellcome Trust said it has been sent to Members of the European Parliament (MEPs) with an interest in science and medicine and to its industry, research and energy committee and environment, public health and food safety committee.

Peter Weissberg, medical director at the British Heart Foundation, said any scaling back of the EU's investment would send out a "dangerous message" that could seriously damage this field "to the detriment of patients in the future".

"The advances in some of the most promising types of stem cell research in recent years, for example the ability to turn adult skin cells into heart cells, have only been possible through the knowledge gained from embryonic stem cell research," he said in a statement.

(Editing by Jon Hemming)

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