David Cameron suffered fresh embarrassment in the NHS row last night when another of his MEPs attacked the service.

The Tory leader spent much of the day engaged in damage limitation, dismissing Daniel Hannan's view that the NHS was a “burden” as “eccentric”.

But another of Mr Hannan's Conservative colleagues in the European parliament risked inflaming the controversy by expressing support for his position.

Interviewed on BBC Radio 4's PM programme, Roger Helmer insisted: “Now we all love the NHS, but I think we all know in our hearts that it is no longer the envy of the world.”

He went on: “If the Americans came to me and said would you recommend us taking up a system just like the British NHS, I think I would have to say ‘No'.”

Labour has been quick to capitalise on Mr Cameron's discomfort, claiming the row exposed “deep ambivalence” within his party towards the health service.

But Mr Cameron insisted he was fully committed to the NHS - which he described as a “great national institution”.

“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.”

He brushed aside the remarks by Mr 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,” Mr Cameron said.

Since he became leader in 2005, Mr Cameron has made much of his own personal commitment to the NHS. Health Secretary Andy Burnham said the Tory leader was “rattled” and Mr Hannan's intervention was his “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.

Business Secretary Lord Mandelson said the public would be shocked to see a Conservative politician flying to the United States to “slag off” the NHS.

Mr Hannan, who is now on holiday in France, was yesterday keeping a low profile.