US negotiators pushed for “full market access” to services including the NHS in talks on a post-Brexit free trade deal with the UK, a cache of leaked documents has revealed.

The papers were dramatically unveiled by Labour leader Jeremy Corbyn, who said they left “in tatters” the prime minister’s denial that the NHS will be on the table in trade talks.

The 451-page dossier of official files showed the US had “pushed hard” to extend patents on drugs developed by American corporations in a way which would raise prices to NHS patients. A UK negotiator said such a move could put Britain “in difficult territory”.

And the dossier made clear that the US has been “emphatic” in its insistence that climate change should not even be mentioned in the deal, which Boris Johnson wants to strike as soon as possible after the UK leaves the European Union.

But furious Conservatives accused Mr Corbyn of “out-and-out lying” and suggested he was peddling conspiracy theories in a bid to distract attention away from his difficulties over antisemitism allegations and Labour’s plans for Brexit and taxation.

General election: On the campaign trail Show all 114 1 /114 General election: On the campaign trail General election: On the campaign trail Boris Johnson drives a Union flag-themed JCB, with the words "Get Brexit Done" inside the digger bucket, through a fake wall emblazoned with the word "GRIDLOCK", during a general election campaign event at JCB construction company in Uttoxeter, Staffordshire AFP via Getty General election: On the campaign trail A sculpture of an owl is bedecked with an EU beret as Liberal Democrat leader Jo Swinson gestures during an interview at a general election campaign event in Bath AFP via Getty General election: On the campaign trail Boris Johnson (C) talks during a question and answer session on a general election campaign visit to Ferguson's Transport in the town of Washington, west of Sunderland AFP/Getty General election: On the campaign trail Boris Johnson tries to save a shot during a warm up before a girls football match while on the campaign trail in Cheadle Hulme, northwest England POOL/AFP via Getty General election: On the campaign trail Jeremy Corbyn makes cup of coffee as he campaigns in Barry, south Wales AFP General election: On the campaign trail Nicola Sturgeon poses as she launches the SNP campaign bus tour, at Queensferry Crossing in Edinburgh, Scotland AFP via Getty General election: On the campaign trail Boris Johnson reacts as he changes a wheel of a Formula One car during a Conservative Party general election campaign visit to Red Bull Racing in Milton Keynes POOL/AFP via Getty General election: On the campaign trail Britain's Prime Minister Boris Johnson visits a Christmas market in Salisbury REUTERS General election: On the campaign trail Liberal Democrat Leader Jo Swinson on the election campaign bus on route to Chelmsford PA General election: On the campaign trail Labour leader Jeremy Corbyn talking to a university worker outside Birkbeck/SOAS University of London, at the announcement of his parties of the plan for the extension of workers' rights PA General election: On the campaign trail Nicola Sturgeon plays a game with string during a visit to Perth and District YMCA Getty Images General election: On the campaign trail Brexit Party leader Nigel Farage picks up a copy of The Brexiteer during a visit to JPI Printers in Dinnington PA General election: On the campaign trail Boris Johnson, centre, talks to veteran James Gammer as he visits a veterans centre AP General election: On the campaign trail SNP supporters meet First Minister Nicola Sturgeon following her address during a St Andrews day election speech Getty General election: On the campaign trail Jeremy Corbyn has a photo taken outside Birkbeck/SOAS University PA General election: On the campaign trail Liberal Democrat leader Jo Swinson during a visit to the Cardiff United Synagogue PA General election: On the campaign trail Brexit Party leader Nigel Farage reacts as he attends an election debate ITV/Reuters General election: On the campaign trail Jeremy Corbyn wears a jacked displaying Labour's slogan 'For the many, not the few' EPA General election: On the campaign trail Prime Minister Boris Johnson on The Andrew Marr Show Getty General election: On the campaign trail Nicola Sturgeon plays with local children during a visit to the Jelly Tots & Cookies Play Cafe in Uddingston, South Lanarkshire PA General election: On the campaign trail Opposition Labour Party leader Jeremy Corbyn eats some chips in Whitby, northern England AFP via Getty General election: On the campaign trail Boris Johnson and Conservative MP George Eustice, left, tour 'Rodda's Clotted Cream' whilst campaigning in Cornwall Getty General election: On the campaign trail Jo Swinson during a visit to Dunkertons Cider Company, an organic and plastic free brewery in Cheltenham PA General election: On the campaign trail Jeremy Corbyn holds up unreacted documents with NHS staff. Mr Corbyn released uncensored official documents which he says provides confirmation that the NHS is on the table in trade talks with the USA EPA General election: On the campaign trail Nigel Farage meets locals in Barnsley market PA General election: On the campaign trail Nicola Sturgeon launches the SNP's general election manifesto Getty General election: On the campaign trail Labour Party leader Jeremy Corbyn addresses the audience during the launch of Labour's environmental policy in Southampton Getty General election: On the campaign trail Boris Johnson tries an apple as he visits Healey's Cornish Cyder Farm in Callestick AP General election: On the campaign trail Jo Swinson helps make a chicken tikka masala during a visit to the Ashoka restaurant in Bearsden, Glasgow PA General election: On the campaign trail Nigel Farage playing golf on a range at One Stop Golf in Hull PA General election: On the campaign trail Jeremy Corbyn addresses the audience during a climate emergency rally in Falmouth Getty General election: On the campaign trail Liberal Democrat leader Jo Swinson meets supporters during a visit to Dunkertons Cider Company PA General election: On the campaign trail Boris Johnson visits Chulmleigh College AP General election: On the campaign trail Labour Party leader Jeremy Corbyn as he appearing on the BBC political programme The Andrew Neil Show. The opposition leader defended his handling of anti-Semitism allegations after Britain's most senior rabbi suggested the issue was a "new poison" within the party that had been "sanctioned from the very top". In an unprecedented intervention ahead of next month's election, Chief Rabbi Ephraim Mirvis suggested Corbyn was "unfit for high office" due to his perceived failure to clamp down on the problem within the party BBC/AFP via Getty General election: On the campaign trail Liberal Democrat leader Jo Swinson alongside Julian Dunkerton, whose father founded and ran Dunkertons Organic Cider, during a visit to the company's organic and plastic free brewery in Cheltenham, Gloucestershire, whilst campaigning for the General Election. PA Photo. Picture date: Tuesday November 26, 2019. See PA story POLITICS Election. Photo credit should read: Aaron Chown/PA Wire Aaron Chown PA General election: On the campaign trail Prime Minister Boris Johnson launches the Conservative Party Scottish Manifesto in North Queensferry Getty General election: On the campaign trail Britain's Opposition leader Jeremy Corbyn poses with WASPI (Women Against State Pension Inequality) supporters after he outlined Labour's plans to repay the "historical debt of honour" owed to women born in the 1950's AFP via Getty General election: On the campaign trail Jo Swinson alongside the Lib Dem's candidate for Truro and Falmouth, Ruth Gripper, and founder of Finisterre, Tom Kay, during a tour of the British surfing brand, which creates sustainable surfing gear, in St Agnes, Cornwall PA General election: On the campaign trail Prime Minister Boris Johnson poses with sheep as he visits the Royal Welsh Showground, in Llanelwedd PA General election: On the campaign trail A coalition of NHS (National Health Service) campaigners led by "Keep Our NHS Public" and "We Own It", pose for photographs with masks of US President Donal Trump, right, and Prime Minister Boris Johnson carving up the NHS with a giant knife and fork, as they take part in a demonstration on Parliament Square. 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PA Photo. Picture date: Tuesday November 19, 2019. See PA story POLITICS Election. Photo credit should read: Stefan Rousseau/PA Wire Stefan Rousseau PA General election: On the campaign trail Liberal Democrat leader Jo Swinson (left) during a visit to the Gurdwara Singh Sabha Temple in Glasgow PA General election: On the campaign trail Labour leader Jeremy Corbyn meets Colin and his mother after a speech at the University of Lancaster Getty Images General election: On the campaign trail Britain's Green Party co-leaders Jonathan Bartley, Sian Berry, and deputy leader Amelia Womack, wave during the launch of the party manifesto at the Observatory at London Wetland Centre Reuters General election: On the campaign trail Scottish Nationalist Party leader Nicola Sturgeon meets voters and activists at Cafe Roma in Clarkston, Glasgow AFP via Getty General election: On the campaign trail Protestors participate in an anti-Boris Johnson rally in his constituency Uxbridge, west London AFP via Getty Images General election: On the campaign trail Brexit Party leader Nigel Farage 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leader Jeremy Corbyn with Laura McAlpine, the party's candidate for Harlow PA General election: On the campaign trail Anti-Boris Johnson protesters demonstrate outside the hall where the Conservative Party were launching their campaign in Birmingham EPA General election: On the campaign trail Green Party Co-Leader Sian Berry (left), Deputy Leader and Parliamentary Candidate for Newport West Amelia Womack (right), and Bristol West Candidate Carla Denyer (centre) at the launch of the party's general election manifesto in Bristol PA General election: On the campaign trail The PM tastes whisky during a visit to Diageo's Roseisle Distillery near Elgin, Scotland Reuters General election: On the campaign trail Nigel Farage poses with boxer Dereck Chisora during a visit to a boxing gym in Ilford Reuters General election: On the campaign trail Jo Swinson visits a science class at Hinchley Wood School near Esher Reuters General election: On the campaign trail First Minister Nicola Sturgeon holds 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Mr Johnson dismissed the Labour leader’s claims as “total nonsense”, and said: “I can give you an absolute cast-iron guarantee that this is a complete diversion. That the NHS under no circumstances would be on the table for negotiation, for sale.”

The row came as new polling data involving almost 40,000 voters suggested Mr Johnson could be heading for a comfortable overall majority of 82, with up to 366 Tory MPs in the 12 December general election.

But analysis of the Focaldata survey* by the Best for Britain campaign for a second referendum suggested that fewer than 120,000 anti-Brexit voters in 57 marginal constituencies could deny Tories a majority by voting tactically.

Mr Johnson’s senior aide and Vote Leave guru Dominic Cummings issued a warning against complacency to Brexit supporters, and said that “things are much tighter than they seem and there is a very real possibility of a hung parliament”.

Mr Cummings said Mr Corbyn aimed to “cheat” a second referendum by extending the vote to foreign nationals, and urged Leavers not to risk letting him into Downing Street by the back door by voting for Nigel Farage’s Brexit Party.

Former Tory MP Nick Boles, who quit the party over Brexit, said the Cummings blog was an attempt to drive up the Tory tally of postal votes, many of which will be cast over the next few days.

After a slew of bad headlines about his refusal to apologise for his handling of antisemitism during a TV interview on Tuesday, Mr Corbyn came back fighting with the claim that Mr Johnson’s government was “preparing to sell our NHS”.

The Labour leader holds up part of the 451-page dossier (EPA)

He pointed to details in the dossier which showed that the US was pushing for a deal in which all services would be opened up to American companies unless they were specifically exempted.

“Total market access” should be the “baseline assumption of the trade negotiations” because it “incentivises freer trade”, the dossier said.

UK officials assured their US counterparts that Britain would be “a liberalising influence” and that together they could “fly the good flag for services liberalisation”.

“That’s a green light for breaking open Britain’s public services so corporations can profit from them,” said Mr Corbyn.

And he warned: “The US is demanding that our NHS is on the table in negotiations for a toxic deal – it’s already being talked about in secret. That could lead to runaway privatisation of our health service.

“Mega-corporations see Johnson’s alliance with Trump as a chance to make billions from the illness and sickness of people in this country.

“And if the Conservatives have their way and this deal goes forward, the changes I’ve revealed will be almost irreversible.”

US President Donald Trump said during his visit to London in June that the NHS would be on the table in trade talks, before hastily backtracking after his comments caused a furore.

Mr Corbyn said drug prices were an average of 250 per cent higher in the US than the UK because of payment regimes, including longer periods when new drugs remain under patent.

And he warned that the NHS could have to pay £500m a week more for medicines under what he termed a “toxic Trump deal”.

Boris Johnson on the campaign trail (Getty)

Mr Corbyn said that as well as healthcare, the documents – which detail meetings over the period July 2017 to July 2019 – showed the talks had covered areas like food safety, workers’ rights and gender discrimination where the US was seeking to tear down UK regulatory barriers.

The document also showed that US negotiators said there would be “all to play for” in a transatlantic free trade agreement if the UK left the EU without a deal with its European neighbours, but that a free trade agreement would be a “non-starter” if Britain remained in the single market and customs union.

Tory sources said healthcare was mentioned in only four parts of the lengthy document, and there was no indication that the UK had acceded to US requests for access to NHS markets. The papers covered a period before Mr Johnson came to office, they said.

International trade secretary Liz Truss said: “Jeremy Corbyn is getting desperate and is out-and-out lying to the public about what these documents contain.

“As we have consistently made clear: the NHS will not be on the table in any future trade deal and the price that the NHS pays for drugs will not be on the table. This sort of conspiracy theory-fuelled nonsense is not befitting of the leader of a major political party.”

Mr Corbyn caused a stir during last week’s TV debate with Mr Johnson by brandishing a document released by the government with most of its contents blacked out, which he said contained the prime minister’s plan “to sell out our NHS to the United States and big pharma”.

On Wednesday, he said he was now able to release the full uncensored version of the reports made by UK officials of their meetings with US negotiators in Washington and London.

But Conservative sources said the unredacted document had in fact been available on the internet for around two months, and suggested Labour had been saving it for use at a time when its election campaign needed a boost.