Cambridge-based pharmaceutical giant AstraZeneca has warned that patients in the European Union might not be able to get medicines from the UK after Brexit.
The company, which is building its new HQ at the city's biomedical campus, says it would need to "prepare well" for a "no-deal Brexit".
AstraZeneca manufactures medicines for treating cancer, heart and lung problems.
Ad Antonisse, the director of market access and external affairs for the company, said it was carrying out tests in both the UK and EU as it prepares for "the strongest Brexit scenario".
Mr Antonisse, told the Dutch government Brexit-loket site: "If we do not prepare well for Brexit, patients in the EU may no longer be able to receive their medicines. Just because production happens to happen in the United Kingdom. Science is simply an international playing field."
Last month, Health Secretary and West Suffolk MP Matt Hancock said officials were considering working with industry to stockpile drugs, medical devices and supplies in the event of a no-deal Brexit.
He said that he was "confident" that a deal could be reached but that it was "responsible" to prepare for a range of outcomes.
This includes working up options with industry to stockpile medical supplies if a deal cannot be reached, Mr Hancock told the Health Select Committee on July 24.