The FT’s science editor Clive Cookson says the pharmaceutical and biotechnology sectors are “shocked by the impending loss of the EU regulatory umbrella, market access and funding” and “will be calling on the government for new incentives to stem what they fear will be an outflow of companies and scientists to continental Europe and beyond”.

Cookson spoke to Mike Thompson, chief executive of the Association of the British Pharmaceutical Industry, who said: “Inward investment stopped about three months ago because of uncertainty about the referendum.”

“We have to be realistic now and accept that people will not invest here until we do something different,” Thompson added.

In a statement AstraZeneca said: “We believe that the UK remaining in the EU would be in the best interests of patients, our industry and our company, but naturally we respect the democratic decision reached in this referendum.

“Clearly, there will now be a protracted period of transition and we will engage with all the relevant stakeholders to safeguard the competitiveness of the life sciences industry and the speed of patient access to innovative medicines.”

GlaxoSmithKline, the other big UK drug company, said: “Although the EU referendum result creates uncertainty and potentially complexity for us in the future, we do not currently anticipate a material adverse impact on the business, group’s results or financial position. We will continue to operate as usual and will engage in the process ahead.”

Jo Pisani, head of pharma and life sciences at PwC, commented: “The pharmaceutical industry now faces a daunting challenge, particularly in terms of regulations for drug development and approvals, intellectual property and investment in the UK.

“In the area of regulations for drug development and approvals, the UK’s impact on EU regulation is likely to diminish, making any UK involvement both more complex and costly or duplicating effort,” she added. “With 7 per cent of the UK’s pharma workforce being non-British, the industry will begin to see obstacles as migration and border controls change.”

The European Medicines Agency, the EU drugs regulator which employs 600 people in London, has said it will have to leave as a result of Brexit.

“It is politically inconceivable that the major European governments will allow the EMA to stay here,” said Mr Thompson. “But the industry will play a role in helping to find an arrangement that allows the EMA to continue working with the UK Medicines and Healthcare Products Regulatory Agency.”