David Cameron has weighed into a transatlantic row to defend the NHS after it came under fire by US critics of President Obama's health reforms.
The Conservatives have sought to reassure voters that the NHS is safe in their hands after one of its MEPs joined in with US attacks on it.
The Conservative leader sent an e-mail to supporters saying millions including his own family were grateful for it.
Daniel Hannan added his voice to criticism of Barack Obama's health reforms, telling US TV he "wouldn't wish" the NHS "on anyone".
It came after the prime minister joined a Twitter campaign and left messages under the tag welovetheNHS.
But Shadow Health Secretary Andrew Lansley said the MEP's comments gave a "distorted" view of the health service.
Meanwhile, a British woman said she felt duped after becoming the unwitting star of an anti-Obama health campaign.
It came as Gordon Brown joined a Twitter campaign to defend the NHS.
Kate Spall, who appeared in a US free market group's TV commercial opposing Mr Obama's health bill, said her views were misrepresented.
'Duped'
She told the Times: "It has been a bit of a nightmare. It was a real test of my naivety. I am a very trusting person and for me it has been a big lesson. I feel I was duped."
Ms Spall and fellow Briton Katie Brickell's descriptions of poor treatment at the hands of the NHS featured in the Conservatives for Patients' Rights (CPR) advert.
Americans give their views on the NHS
But the two women say they support state-funded healthcare and thought their comments were to be used on a documentary examining reform.
Mr Cameron's e-mail said Britain was proud of the NHS and he would spend more on the service, but also make it more efficient and responsive to patients.
He is the latest leader to step into the row after Gordon Brown and his wife Sarah left Twitter posts saying the NHS "often makes the difference", adding "thanks for always being there".
The Twitter campaign has attracted more than a million followers and thousands of messages of support - including from Health Secretary Andy Burnham and former deputy prime minister John Prescott.
US critics of Mr Obama's reforms have cited the NHS as an example of an overly bureaucratic "socialised" system which rations care and denies treatment to the elderly.
One US newspaper claimed NHS rationing meant Professor Stephen Hawking, who has motor neurone disease, "wouldn't have a chance in the UK".
But during a visit to Washington to collect an award, Mr Hawking hit back saying: "I wouldn't be here today if it were not for the NHS."
Mr Cameron's comments followed those of Tory MEP Daniel Hannan, who told US TV he "wouldn't wish" the NHS on anyone.
Shadow health secretary Andrew Lansley has since said Mr Hannan did the NHS a "disservice" by giving Americans "such a negative and partial view".
