In a press conference in Westminster, Mr Corbyn brandished what appeared to be leaked government papers detailing six rounds of trade talks in Washington and London running from July 2017 to a few months ago.
He said that the content of the 451-page paper left “in tatters” prime minister Boris Johnson’s denial that the NHS is on the table in trade talks.
And he declared: “This election is now a fight for the survival of our National Health Service as a public service free for all at the point of need.
“So for the want of any doubt, let me give this reassurance: Labour will never ever treat our NHS as a bargaining chip in trade talks with anybody. We will never let Donald Trump get his hands on our NHS. Because our NHS is not for sale.
The bombshell announcement came as Mr Corbyn battled to force the general election agenda back onto his preferred turf of health, after a nightmare day on Tuesday in which his fitness to govern was questioned by the Chief Rabbi and he refused four times in a difficult BBC interview to apologise for his handling of antisemitism in his party.
In a tweet, the Labour Party said that the unredacted documents “show Boris Johnson’s government is preparing to sell our NHS”.
However, all of the meetings detailed in the documents took place before Mr Johnson became prime minister. The memos record discussions between July 2017 and July 2019, under Theresa May's government.
The Tories accused Mr Corbyn of "out-and-out lying to the public" and peddling "conspiracy theories".
Mr Johnson has previously said there “no circumstances whatsoever” in which a Conservative government would put the NHS on the table in trade talks with the US.
However, Mr Corbyn said he said: “What I have here is… 451 pages of unredacted documents and information …which is a very different version of events.
“Perhaps he would like to explain why these documents confirm the US is demanding the NHS is on the table in the trade talks.
“These uncensored documents leave Boris Johnson’s denials in absolute tatters. Voters need to ask themselves some very serious questions – Is the NHS safe in Boris Johnson’s hands?
“We’ve now got evidence that under Boris Johnson, the NHS is on the table and will be up for sale. They tried to cover it up. Their secret agenda today is exposed.”
Mr Corbyn said that the documents showed that Mr Johnson’s promise to “get Brexit done” was “a fraud on the British people”.
He said they made clear that US corporations were seeking to force up the prices the NHS pays for drugs and to extend the duration of patents which allow the companies to maximise income from their medicines.
“Negotiations have advanced even further than we feared they had,” he said. “The US and the UK have already finished initial discussions on lengthening patents for medicines.
“Longer patents can mean only one thing – more expensive drugs. Lives will be put at risk as a result of this.”
UK officials had reported that their US counterparts want "total market access” as the “baseline assumption of the trade negotiations”. And they said that the US could expect the UK to be "a liberalising influence” and that together they could “fly the good flag for services liberalisation”.
Mr Corbyn said: "That’s a green light for breaking open Britain’s public services so corporations can profit from them."
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."
He said that as well as healthcare, the documents 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.
And they show an absolute refusal from Washington for climate change to be mentioned in any final deal, he said.
Mr Corbyn said: "It seems to me that it’s now on Boris Johnson to explain how all of this is an 'absolute invention'... To explain why he denied the very things we can now read in black and white. He must now come clean about the Conservatives’ sell-out plans for our NHS."
Responding to the claims, Liz Truss, the international trade secretary, said: “Jeremy Corbyn is getting desperate and is out-and-out lying to the public about what these documents contain. He has always believed in conspiracy theories - which is why he has failed to crack down on the scourge of antisemitism in his party. This is the man that has caused huge offence by blaming an imaginary ‘Zionist lobby’ for society’s ills and now he has decided to smear UK officials too.
“People should not believe a word that he says - this stunt is simply a smokescreen for the fact that he has no plan for Brexit and that he has been forced to admit that he wants to increase taxes for millions of families.
“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.”
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