Critics say it could leave the UK vulnerable to shortages of medicine, staff, and funding in the years ahead

With the United Kingdom on the verge of crashing out of the European Union without a post-separation trading deal in place, the government is encouraging the nation's businesses to prepare for a bumpy transition. But, while the economic disruption of a no-deal Brexit is likely to be massive, some observers fear it would pale into insignificance next to the chaos that could befall the National Health Service, where such an exit could be a matter of life and death.

Jonathan Ashworth, the opposition Labour Party's health critic, said after reading a recent analysis of the risks, which include potentially cancelled surgeries,that the government's attitude was "bewildering".

"From delays in accessing lifesaving drugs, to the desperate staffing implications that our already understaffed and overstretched NHS faces, this report makes crystal clear the sheer irresponsibility of refusing to rule out no-deal," he said.

But Health Secretary Matt Hancock has attempted to reassure worried patients that medicines imported from Europe will remain readily available, no matter what tariffs and choked borders may follow.

He said months of planning mean the NHS will continue to run smoothly, "if everyone does what they are supposed to".

And Stephen Hammond, a minister in the Department of Health and Social Care, added that the government has analyzed the supply chains of 12,300 medicines and believes there will not be shortages.

"While we never give guarantees, we are confident that, if everyone – including suppliers, freight companies, international partners and the health and care system – does what they need to do, the supply of medicines and medical products should be uninterrupted in the event of exiting the EU without a deal," he said.

A government source told the Guardian preparations include a new"logistics hub in Belgium" to ensure "vital medical supplies will be stockpiled to stop the NHS running short of equipment if there is a no-deal Brexit".The health service is also understood to be planning to use seven new ferry routes in an attempt to bypass gridlock at the Port of Dover.

And the government has made encouraging noises about making it easier for doctors, nurses, and other healthcare professionals to get visas to work in the UK after the freedom of movement of EU nationals ends.

But the assurances and leaked stories have failed to calm everyone's nerves.

A Sky News investigation found many senior managers in the NHS were uncomfortable with the situation.

The broadcaster filed a Freedom of Information request with NHS trusts to find what was being said around boardroom tables and found, in addition to concerns about possible shortages of medicines, and staff, and disappointment about not being allowed to stockpile medicines locally, that many were bemoaning a lack of information from the Department of Health and NHS England.

It was this lack of information that prompted Labour Party MP Rushanara Ali to ask the government about rumors she had heard of pharmaceutical organizations being compelled to sign non-disclosure agreements.The government confirmed there were 26 such "gagging orders" in place.

"It is utterly unacceptable for the government to use non-disclosure agreements with pharmaceutical businesses and trade associations," she said in Parliament. "By effectively 'gagging' these organizations, these secretive agreements are preventing essential information from being shared, undermining transparency, and hampering businesses' ability to speak out."

The risks posed by a no-deal Brexit were probed in an article published in late February in The Lancet medical journal, which said all forms of Brexit would negatively impact the NHS, but that a no-deal exit would be worst of all.

The team of experts in public health and law that carried out the review said that, in addition to shortages of medicines and staff, the NHS is likely to suffer financially because of reduced opportunities to seek funding from the European Investment Bank, and lamented an expected inability to share information and collaborate on medical research.

"Our analysis shows that a no-deal Brexit is substantially worse for the NHS than a future involving the withdrawal agreement," the report writers wrote, while warning that "little evidence exists that the UK is prepared for any of the eventualities".

They said the government's recently published 136-page 10-year plan for the NHS only mentions Brexit twice and does not consider "what it might mean or how any threats would be addressed".

Professor Martin McKee, from the London School of Hygiene and Tropical Medicine, who was one of the report's authors, said: "Some people will dismiss our analysis as 'Project Fear'. But … we need to move beyond slogans.We have set out the problems in detail, based on the best available evidence."

He said the lack of detail from government was regrettable.

"It just isn't good enough to keep saying that 'something will work out' without any details of exactly how," he said.

A no-deal Brexit will also derail reciprocal health arrangements that entitle British people to free healthcare in EU countries, and EU citizens in the UK to the same. The European Health Insurance Card will not be recognized in the event of a no-deal Brexit.

Amber Kirby, who owns an apartment in Spain, says the issue is worrying.

"It remains to be seen what will spin out but I believe people will have to look at private health alternatives," she said. "I'm seriously considering getting my Irish passport, so I can still benefit from the European Health Insurance Cards we currently have."

And if the UK crashes out without a deal, the UK will no longer be a member of the European Medicines Agency, which will make it less attractive to pharmaceutical companies as a place to conduct research or manufacture products.

Healthcare professionals and patients are likely to show a healthy interest in how events unfold during the next few days.