Sarah Brown has joined the campaign to defend the NHS
Gordon and Sarah Brown have joined a Twitter campaign to defend the NHS, which is under fire in the US.
The prime minister posted a message on the welovetheNHS page after critics of Barack Obama's health reforms dubbed it "Orwellian" and "evil".
Mr Brown said the service "often makes the difference", and added "thanks for always being there".
Meanwhile, a Tory MEP who told US TV he "wouldn't wish" the NHS on anyone, has been rebuked by the party.
Conservative officials said Daniel Hannan had done the NHS a "disservice" by giving Americans "such a negative and partial view".
The Twitter campaign has attracted more than a million followers and thousands of messages of support - including tweets from Sarah Brown, who wrote welovetheNHS "more than words can say", Health Secretary Andy Burnham and former deputy prime minister John Prescott.
On Wednesday evening a message was posted on it from the Downing Street Twitter feed, saying: "PM: NHS often makes the difference between pain and comfort, despair and hope, life and death. Thanks for always being there".
Many of the tweets in support of the NHS are from members of the public saying they owe their families' or their own lives to its care.
Professor Stephen Hawking has also hit back at claims in American newspaper that NHS rationing would mean he "wouldn't have a chance in the UK", saying on a visit to Washington to collect an award: "I wouldn't be here today if it were not for the NHS".
The NHS has been held up by opponents of Barack Obama's health reforms as an example of an overly bureaucratic "socialized" system which rations care and denies treatment to the elderly.
Mr Obama's critics claim he would set up "death panels", a reference to the UK's National Institute for Health and Clinical Excellence, which decides which drugs receive funding.
Republican former vice-presidential candidate Sarah Palin said such a system was "downright evil".
Tory MEP Daniel Hannan, who has long campaigned for the NHS to be dismantled and replaced with a system of "personal health accounts", has joined in the criticism on US television, where he described it in April as a "60-year mistake".
Speaking on Fox News on Friday, Mr Hannan continued his criticism.
"The most striking thing about it is that you are very often just sent back to the queue," he told the Glenn Beck programme and spoke of elderly patients "left starving in wards".
He described the NHS as a product of wartime planning, like rationing, and added: "I find it incredible that a free people living in a country dedicated and founded in the cause of independence and freedom can seriously be thinking about adopting such a system in peacetime and massively expanding the role of the state when there's no need."
Mr Hannan gained worldwide fame on YouTube earlier this year with a strongly-worded attack on Gordon Brown in the European Parliament, which earned him a strong grassroots following among Conservative members and a high-profile speaking slot at the party's spring conference.
The party leadership has taken a dim view of his latest media appearances - but it has stopped short of formally disciplining him.
Shadow health secretary Andrew Lansley said: "There are millions of people who are grateful for the care they have received from the NHS.
"It does them and the NHS a disservice for Daniel Hannan to give Americans such a negative and partial view.
"That we can access healthcare free at point of use, based on need, is something others envy. Our task is to ensure that the quality of care is consistently excellent.
"And the service is efficient and responsive to patients. Choice, competition and information, focused on outcomes, will deliver this".
Tory leader David Cameron, who has pledged to protect the health service from public spending cuts, also sought to distance himself from Mr Hannan's comments when he was tackled about them on a walkabout in his constituency.
He told BBC News: "I support the NHS 100% and the Conservative Party supports the NHS 100%.
"We are the party that gives the biggest amount of support to the NHS. It is incredibly important to my family. It is incredibly important to this country."
He vowed to "nurture the NHS" if he came to power, "and improve it and make sure it is there for everyone in this country".
Writing on his Daily Telegraph blog, Mr Hannan said he was a strong supporter of Mr Cameron, but disagreed with him on health.
"I am not the Conservative Party's healthcare spokesman. I'm fond of (shadow health secretary) Andrew Lansley, and I strongly support David Cameron as party leader. On this issue, though, I disagree with both of them."