Britain leaving the European Union could lead to the “break-up” of the NHS, one of the world’s leading Brexit experts has told The Independent.

Professor Alex de Ruyter, director of the Centre for Brexit Studies at Birmingham City University (BCU), warned any future trade deal with the US would mean American pharmaceutical companies looking to access the health service.

His warning comes just months after Theresa May stoked fears of an NHS “for sale” in a future trade deal with the US, after she refused to say it would be excluded from talks.

“The NHS is the biggest market for drugs, probably in the world,” Mr de Ruyter said. “It basically sets the price of pharmaceuticals in Europe. So outside of the EU, big pharma in the US will obviously want access to that, so you potentially could see the break-up of big chunks of the NHS.”

Warning about future trade disputes between Britain and America, the former director of BCU’s business school said the UK faced the prospect of opaque arbitration panels once it leaves the European Court of Justice‘s jurisdiction.

“They generally side with the company lodging the complaint against what they regard as anti-competitive government behaviour,” Mr de Ruyter said. ”Now, in the eyes of an American pharmaceutical company, the NHS is the ultimate anti-competitive government body.”

“We may have to compromise on the NHS, and open up tenders for NHS products and services to private sector competition,” he added.

David Davis wants post-Brexit relationship with Europe that 'recognises the history' and 'stands the test of time'

Research earlier this year revealed the proportion of health service contracts being won by non-NHS firms ballooned by almost 70 per cent in 2017. Private care providers were awarded 267 out of a total of 386 contracts made available in 2016-17 – taking spending up by £700m to £3.1bn.

Critics say this rising “privatisation” has already opened the door to US health firms, who view the NHS as a gold mine – even before talks on a trade deal after Brexit.

In February, Donald Trump gave a flavour of his thoughts on the NHS. “The Democrats are pushing for Universal HealthCare while thousands of people are marching in the UK because their U system is going broke and not working,” he tweeted.

America “doesn’t need a trade deal in the way that a post-Brexit UK outside of the customs union does”, Mr de Ruyter said.

“If you want a trade deal with the US you’ll have to embrace their framework. They’re not going to budge from that, they think they’re the superior negotiating party here, and to all intents and purposes they are.”

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Mr Trump, he said, is “not really focused” on Britain, but on the “big beasts” of the global economy such as China and the EU.

“The UK is just another would-be supplicant country coming along knocking on the door wanting an arrangement.”

Mr de Ruyter also warned there was going to be no easy way to heal divides between Remain and Leave voters, regardless of any final settlement.

“There’s no evidence out there that people have moved on, and bringing them together implies that you can talk to each other, whereas people seem today even more entrenched in their views,” he said.

Despite the vote for Leave, he said there was “maybe a one in 10 chance” the country would remain in the EU. “I wouldn’t rule it out,” he added.

He condemned Ms May for her “have your cake and eat it” approach to negotiations with Europe, and warned the government were sooner or later going to have to choose between a clean break or a deal that would leave arch-Brexiteers unhappy.