LONDON (Reuters) – The number of new clinical trials started in Britain last year was 25 percent lower than the average for 2009-16, as anxiety about Brexit’s impact on future medicines regulation made companies hesitate about running studies in the country.

A total of 597 trials were initiated in Britain in 2017, against an average of 806 over the previous eight years, according to a Fitch analysis on Tuesday.

Drugmakers’ confidence has been dented by fears research data collected in Britain might not be acceptable to the European Medicines Agency (EMA) after the UK leaves the European Union next March.

The pharmaceuticals industry has long warned that Brexit could have a serious impact on research and access to medicines, unless London and Brussels hammer out a deal for regulatory continuity and close liaison with the EMA.

If there is no deal, the UK’s Medicines and Healthcare products Regulatory Agency would have to operate as a stand-alone regulator and there is no clarity over how UK data would be treated by the EMA.

Historically, the UK’s National Health Service (NHS) has been an important center for drug research, a backdrop that has encouraged pharmaceutical investment. Now industry leaders fear this could be at risk.

“We know from our members that Brexit-related uncertainty is a major concern when it comes to decisions about whether to set up trials in the NHS,” said Sheuli Porkess, deputy chief scientific officer at the Association of the British Pharmaceutical Industry.

“This is why it’s vital that we get a Brexit deal to keep the investment and skills in clinical trials here in the UK.”

Concerns over the issue were highlighted last week by news that U.S. biotech company Recardio had suspended trials of a new heart drug in Britain.

(Reporting by Ben Hirschler, editing by Louise Heavens)