Pharmaceutical giant AstraZeneca has said patients in the European Union may not be able to receive vital medicines from the UK if the company does not successfully prepare for a no-deal Brexit.

The manufacturer of cancer, heart and lung drugs told an official Dutch government website that it was going to have to test medicines in both the UK and the EU to ensure they could cross the border in all Brexit scenarios.

But AstraZeneca conceded that it could not guarantee it would succeed, and emphasised that in its case it could be EU citizens who will be at risk, because many of its drugs are manufactured and quality tested in the UK.

Ad Antonisse, the company’s Dutch external affairs director, told the Brexitloket website: “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.”

Ministers have repeatedly talked up the possibility of a no-deal Brexit over the past month as the UK attempts to persuade the European Union that it could walk away unless there is a breakthrough in talks, which have stalled over trade and customs arrangements.

Professor Jean McHale, a health care law specialist at Birmingham University, said: “Access to medicines and drugs is one of the most important healthcare issues that will have to be dealt with in an no-deal Brexit scenario. The government has to ensure there will be some sort of reciprocal arrangement to ensure smooth movement of drugs across borders.”

AstraZeneca is one of the world’s leading pharmaceutical companies, employing 6,700 people in the UK, and running its worldwide research from Cambridge. It specialises in oncology drugs to treat cancer as well as treatments for respiratory and cardiovascular conditions.

“These are serious diseases and you don’t want Brexit to have a problem with delivery to the patient,” Antonisse said, adding: “We are therefore preparing for the hardest Brexit scenario.”

At present, the company only has to quality test drugs it has manufactured once in the EU to ensure it can be distributed around all member states. However, it is setting up a parallel testing operation in Sweden, an EU member state, so that it can ensure that medicines can be distributed in both the UK and the EU in case reciprocal regulatory arrangements are not agreed after Brexit. It carries out around 5,000 such tests a year.

“We are now carrying out these tests twice, both in the UK and in Sweden – an EU country, because the UK will soon be out of the EU. We also have to do tests if substances from the EU go to the UK,” Antonisse said.

AstraZeneca has spent around £40m on the effort to deal with Brexit. Last month, Pascal Soriot, the company’s chief executive, said that it was increasing its stockpiles of medicine in the UK and Europe to deal with the no-deal Brexit scenario that government ministers have been talking up. It will warehouse four months’ worth of drugs in the run-up to Brexit day in March 2019.

Last month, health secretary Matt Hancock said that the NHS would be prepared for a no-deal Brexit scenario. “We are working right across government to ensure that the health sector and the industry are prepared and that people’s health will be safeguarded in the event of a no-deal Brexit,” Hancock told MPs.

Polling conducted by ICM for the Guardian suggests that only 16% of the public believe that a no deal would be the best outcome for the country, as opposed to 42% who believe that the UK should leave the EU with some sort of deal. A further 31% said that the best outcome would be staying in the EU following a second referendum.

The same poll, carried out between 3 and 5 August, showed Labour at 40%, one percentage point ahead of the Conservatives at 39% although both parties were down a percentage point from the last ICM survey two weeks earlier. The Lib Dems polled 7%, also down one percentage point, while Ukip gained a percentage point to reach 6%.