Thousands of UK citizens, including community group and trade union members, took part in a demonstration in central London on Saturday, celebrating the National Health Service and demanding that all political parties uphold its principles of care.

The organisers said that over 7,000 staff took part in the “I Love The NHS” event, which finished in Trafalgar Square.

In the latest twist in internet based campaigning, many hundreds of people pledged to attend the day on the social networking site Facebook.

Dr Hamish Meldrum, chair of the British Medical Association’s council, and a Bridlington general practitioner, said: “As GPs, we’re saying stop blaming us for the NHS’s problems.”

Trades Union Congress (TUC) president David Prentice told the rally that the service must not be “sold off to private companies”.

Karen Jennings of the Unison union said Britain should cherish a health service free at the point of need, available to all, and paid for by redistributive taxation.

Ms Jennings told BBC News: “We’re coming up to its 60th anniversary, and we’re very keen to get the message across that we’ve got quite an extraordinary health service in this country.”

She said despite criticisms by politicians and the press, surveys have shown that the vast majority of people who use the NHS are very satisfied with it.

The Unison spokeswoman declared: “[In m]any, many comparable countries, their citizens really fear having to pay for their healthcare and whether they can afford it, and we don’t have these worries here.”

She continued: “We’ve got something that is a very precious resource here and we shouldn’t undermine the ethos that exists, and the founding principles on which the NHS is based.”

Mrs Jennings said she was “very worried” about plans by the Conservatives to introduce more competition into the health service.

She explained: “The big fear that staff working on the NHS have, and many, many local communities, is that you fragment the NHS if you make it too competitive.”