Life sciences leaders are warning that Britain's departure from the European Union will bring uncertainty to the industry, creating new barriers to inward investment and threatening access to novel medicines.

In a letter to The Observer, more than 90 signatories - including heads of the Association of the British Pharmaceutical Industry, GlaxoSmithKline, AstraZeneca and the BioIndustry Association - argue that the future success of the UK life sciences sector is underpinned by being part of the EU's single market and regulatory processes.

If the UK was to bow out of a reformed Europe, companies could be forced to apply for separate market authorisations in both regions - which could delay access for the millions of NHS patients to the latest drugs and treatments, they warn.

"We are concerned that the lack of clarity around what would happen to the regulation, patents ecosystem, financing and funding for UK bioscience if the UK were to leave the EU creates risk and uncertainty that could undermine the future success of the sector," said Steve Bates, chief executive of the BioIndustry Association. "It's vital the UK remains engaged in the EU to influence legislative and regulatory policy developments affecting the life sciences ecosystem."

"This is a serious warning from the leaders of the UK's £60 billion life science sector, which highlights the choice in this referendum: our economic security and global influence as part of the EU, or a leap in the dark," noted life sciences minister George Freeman. "Being out on our own would risk the employment of 220,000 people, billions of pounds of inward investment, and our life science exports to the EU - which last year were worth over £29 million every day."

Recently writing in a blog for Deloitte, Karen Taylor, Director, UK Centre for Health Solutions, notes that the UK currently receives more funding from the European Research Council than any other EU country, which supports universities' research. "One government minister has told Parliament's Science and Technology Committee that Brexit could threaten £8.5 billion of EU funding for UK science over the next four years. There is also a risk that UK researchers will lose their priority access to scientific facilities across Europe," she writes.

The letter concludes that "remaining in a reformed and more competitive EU would offer stability and predictability as a platform for even greater success. Staying in would be better for the health and wealth of the UK."

The Brexit camp hasn't said much about the impact on life sciences industry directly, but campaigners have argued that the NHS is at risk from staying in the EU, largely because of the proposed Transatlantic Trade and Investment Partnership (TTIP) between the EU and the US, and also health tourism, which the Vote Leave group claims is costing the UK £700 million a year.

The British public will vote on whether or not to stay in the EU on June 23.