Gordon and Sarah Brown have joined an online campaign defending the NHS from attacks in America.
The couple posted messages on social networking site Twitter after the service was condemned by Republicans as "evil and Orwellian".
Health Secretary Andy Burnham also offered support - although he risked embroiling himself in controversy by joking he was more interested in his football team than the NHS.
President Barack Obama's plans for reforming healthcare have sparked a furious row on the other side of the Atlantic. Opponents have warned that the changes will "socialise" the system, and could even lead to panels deciding whether the elderly deserve life-saving treatment.
The welovetheNHS campaign was launched by Britons keen to counter the allegations, and the sheer number of messages added apparently crashed the Twitter site on Wednesday.
UK politicians are generally wary of wading into domestic policy rows in the US.
But among the missives was one from Downing Street stating: "PM: NHS often makes the difference between pain and comfort, despair and hope, life and death. Thanks for always being there." Mr Brown's wife added her own comment, saying: "#welovetheNHS - more than words can say."
A message posted on Mr Burnham's behalf by Downing Street said: "Andy Burnham: Over the moon about strong support for NHS - an institution I will defend to my dying day, 2nd only to Everton FC."
Renowned physicist Stephen Hawking, who has motor neurone disease, rejected criticism of the NHS yesterday as he collected America's highest civilian honour, the Presidential Medal of Freedom. "I wouldn't be here today if it were not for the NHS," Prof Hawking said.
Prof Hawking was commenting after one US commentator suggested he would be left to die under the UK system. The claim, in an editorial yesterday for Investor's Business Daily, was later corrected after the newspaper realised that the renowned scientist was born, lives and works in the UK.
