US President Donald Trump has triggered another extraordinary spat with Theresa May's government after claiming the NHS was "going broke and not working".
Health and Social Care Secretary Jeremy Hunt hit back by saying he was "proud" of the British system despite the "challenges" it faced.
The US president said "thousands of people are marching" in the UK because of concerns about the state of the NHS.
Mr Trump made the attack as he targeted Democrats pushing for a British-style universal health system in the US.
But Mr Hunt responded to Mr Trump's Twitter attack with a post of his own, saying no-one protesting about the state of the NHS wanted a US-style system.
"NHS may have challenges but I'm proud to be from the country that invented universal coverage - where all get care no matter the size of their bank balance," he said.
The US president's comments were also condemned by Labour leader Jeremy Corbyn and the organisers of the NHS demonstration highlighted by Mr Trump.
The president's comments came shortly after former Ukip leader Nigel Farage appeared on one of Mr Trump's favourite US TV news shows to talk about the NHS.
Mr Farage's appearance on Fox And Friends appeared to be the reason for Mr Trump's Twitter comment.
In a follow-up message, the president thanked the show for "exposing the truth".
Mr Trump's social media messages came after a crowd of thousands chanting "Save the NHS" descended on Downing Street on Saturday to demand more funding for the health service.
The demonstration, called NHS In Crisis: Fix It Now, was organised by the People's Assembly and Health Campaigns Together.
Responding to Mr Trump's comments the groups said they were campaigning against moves to an "expensive, inefficient and unjust" US-style system.
In their message to Mr Trump, the groups said in a statement: "This is what our demonstration was about on Saturday February 3 and tens of thousands of British people want to show their love for the principles of universal and comprehensive care free at the point of use, paid for through general taxation.
"We don't agree with your divisive and incorrect rhetoric. No thanks."
Labour leader Jeremy Corbyn said Mr Trump was "wrong" and people were marching because "we love our NHS and hate what the Tories are doing to it".
The public row with Mr Hunt is the latest controversial episode in Mr Trump's presidency ahead of a UK visit later this year which is expected to be marked by mass protests.
He had previously caused consternation in Whitehall when he announced on Twitter he would not be attending the opening of the new US embassy in London, saying it was a "bad deal" and he did not like the location of the new building.
It led to speculation he was unhappy after being rebuked by Mrs May for retweeting videos posted by the far-right Britain First group.
However, following his talks with Mrs May in Davos, Mr Trump reaffirmed his commitment to the "special relationship" with Britain.