David Cameron today slapped down a Tory MEP who went on American television to attack the National Health Service, dismissing his views as "eccentric"
The Conservative leader said the NHS was a "great national institution" and that it was his party's "number one mission" to improve it.
"The Conservative Party stands four square behind the NHS," he told reporters in his Oxfordshire constituency.
"We are the party of the NHS, we back it, we are going to expand it, we have ring-fenced it and said that it will get more money under a Conservative government, and it is our number one mission to improve it."
Mr Cameron brushed aside an attack on the NHS's record by Tory MEP Daniel Hannan, who told American television viewers that he "wouldn't wish it on anybody".
"He does have some quite eccentric views about some things, and political parties always include some people who don't toe the party line on one issue or another issue," the Tory leader said.
However, Labour was quick to exploit Mr Hannan's remarks, with Business Secretary Lord Mandelson claiming that they had exposed the "two faces" of the Conservative Party.
"I think people will find it shocking that a Conservative parliamentarian should go to the US in order to slag off the NHS, which is one of our great achievements in this country," he told Sky News.
"What we see is the two faces of the Conservative Party - the one David Cameron wants to everyone to see and believe, and the other one presented by the Conservative parliamentarian."
Health Secretary Andy Burnham said Mr Hannan's intervention was Mr Cameron's "worst nightmare".
"What has happened within the last 48 hours is what Cameron has feared most because it lays bare the Tories' deep ambivalence towards the NHS," he said.
"Their election strategy is not to talk about the NHS. Cameron knows there is deep hostility towards it within his ranks. Hannan is not the only one - many senior Tory MPs would privately agree with his comments."
The latest controversy has been sparked by President Barack Obama's plans to reform the the American healthcare system.
Republican critics have used the example of the NHS to attack the president's proposals, branding them as "Orwellian" and "evil".
That in turn has prompted a backlash in Britain, with thousands of people, including Prime Minister Gordon Brown and his wife Sarah, sighing up to an online Twitter campaign to defend the NHS.
Speaking at a press announcement at aircraft manufacturer Airbus's plant in Filton, Bristol, Lord Mandelson defended the NHS.
The Business Secretary said: "I think people will be shocked by the attacks being launched on the NHS in the US - which now, we hear, are being supported by some in the British Conservative Party as well.
"This is a Conservative Party that says it is committed to the NHS, and produces fine words to support that.
"But then, when you look at the facts, you see the Conservatives are not committed, for example, to our opening up of GPs' facilities and wider access, they're not committed to our lower waiting times for cancer treatment, and they don't support the new personal patient entitlements that the Government is introducing.
"Their attitudes and beliefs to the NHS seem to be rather different."
Mr Hannan has made a series of high-profile appearances on Fox News in the United States this year attacking the NHS.
This week he said the cost of the NHS had left the British economy close to collapse, like that of Zimbabwe.
He said: "We're maybe a couple of years behind Zimbabwe, a few years ahead of you.
"I mean, it's - we have - the healthcare system we have is kind of a relic of an era in Britain when the State was considered all-powerful and benign and when we had rationing and when we had ID cards and when we had mass nationalisation.
"And we're still stuck with it because, once you get a system like that, it's almost impossible to get rid of.
"How amazing to me that a free people, you know, citizens of a country founded on the principle of independence, independence for the citizen as well as independence for the state, should be contemplating, in peacetime, burdening themselves with a system like this, which puts the power of life and death in a state bureaucracy."
He added: "People are left in pain, in positions where they can't work, where they're losing income at the back of the queue, waiting for permission to get treatment.
"And there's nothing you can do about it."