Brexit could drive up the cost of medicines for UK patients and the NHS and put at risk access to treatments, a parliamentary report has warned.
The UK pharmaceutical industry also risks losing its status as a world leader in the sector unless a good deal is secured, the Commons Business Committee said.
The cross-party committee called on ministers to deliver a deal for the sector that keeps the closest possible regulatory alignment with the EU and the minimum possible border friction for its products.
Its report said the UK should seek, as a priority in negotiations, a continued form of membership of the European Medicines Agency, which is moving from London to Amsterdam as a result of Brexit.
Divergence from EMA regulations would mean pharmaceutical companies having to duplicate facilities and roles in the UK and EU if they wish to sell into both markets, imposing extra costs of as much as £45,000 on each new product released, the report warned.
This would make the UK "an unattractive market for new and innovative medicines", the committee said.
Leaving the EU without an agreement for the industry would diminish access to markets, including £11.9 billion of exports and more than 446 million potential patients, the report warned.
British patients' access to medicines would also be at risk, with nearly three-quarters of pharmaceutical imports coming from the EU.
Barriers to trade and duplicated regulations could lead to higher prices, with the NHS and consumers expected to pick up the bill or risk reduced access to medicines.
Committee chair Rachel Reeves said: "The Government's own analysis identifies pharmaceuticals as the sector for which UK/EU market access is the most important, given the industry is reliant on friction-free border movement for their products.
"Any delays at the border faced by short-life pharmaceuticals for emergency treatments would have a hugely detrimental impact on patients.
"The Prime Minister has previously set out a positive and compelling case for continued cooperation on medicines, but - with the clock ticking - it is now time for the Government to end the uncertainty and translate words into actions.
"Some form of membership of the EMA is vital to the continued success of the pharma industry and to the welfare of British patients, and the Government should strike a deal to keep some of the organisation's jobs and facilities in the UK, to continue to share our world-leading expertise.
"The Government must do all it can to reach an agreement that not only protects the UK's status as a world leader for pharmaceuticals but also allows patients across the continent to continue to be provided with the medicines they need."
A spokesman for the Department of Health and Social Care said: "The UK's world-leading pharmaceutical industry continues to thrive and we are committed to doing all we can to ensure the sector remains competitive after we leave the EU.
"It is also vital that UK patients have timely access to safe medicines and medical innovations, which is why the PM made clear in her Mansion House speech her ambition for the UK to continue its close working relationship with the European Medicines Agency."
In a joint statement, the Association of the British Pharmaceutical Industry and the UK BioIndustry Association said: "Every month, 45 million packs of medicine move from the UK to the EU, with 37 million moving the other way.
"Today's select committee report is right - a Brexit 'no deal' would significantly damage public health, patient access to medicines and the UK's leading pharmaceutical sector. This must be avoided at all costs.
"Securing co-operation on the regulation, trade and supply of medicines must be a priority for both the UK Government and the EU."
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