Thousands of nurses, midwives, doctors, physiotherapists, and other NHS workers are thought to have attended the rally

The defiant tone was set at the start of Save our NHS rally at Westminster's central hall when the crowd gave a noisy standing ovation to June Hautot, the veteran NHS campaigner who made headlines last month when she cornered Andrew Lansley as he tried to get into Downing Street for the prime minister's NHS summit, from which most key medical organisations were excluded.

It was just one of many low points the health secretary has experienced during the health and social care bill's tortuous and highly charged 14-month progress.

Thousands of nurses, midwives, doctors, physiotherapists, cleaners, porters and other NHS workers were thought to have attended the rally, with marches from the headquarters of the British Medical Association near Euston and St Thomas's hospital in south London converging on Westminster.

The atmosphere was optimistic; the talk was of fighting the bill – and getting it dropped. Only Andrew George MP, the most awkward of the Liberal Democrats' parliamentary awkward squad on the bill, was jeered, and that was because of the party he represents.

But when the crowd was told that he had campaigned against the plans from the start, that turned to applause, though punctuated by increasingly angry cries that his party was selling out the NHS.

Speaker after speaker stressed their love and admiration for the NHS and its unique place in national life. "It's more popular than the BBC and more popular than the royal family," said Dave Prentis, the general secretary of Unison. Kailash Chand, the doctor behind the e-petition on the Downing Street website, which has gained a record 170,000 signatures, demanding the scrapping of the bill, said it was "the finest achievement of the 20th century".

Vikki Mills, who is experiencing plenty of NHS care as she is pregnant with twins, said she had been told that her babies may be born prematurely and need special care. "My care is based on my needs," she said, before warning that the coalition's plan to let NHS hospitals raise as much as 49% of their income from private patients could lead to a two-tier NHS, with some patients getting better care than others simply because they were paying for it.

Then she took on Lansley's common refrain that critics of the bill oppose it because they do not understand it. "David Cameron, Andrew Lansley, Nick Clegg, I'm against this bill because I do understand it", Mills said, to loud applause.

Nye Bevan's famous dictum that the NHS would survive for as long as there was people left to fight for it was invoked over and over again, gaining applause every time.

Comedian Jo Brand, an ex-psychiatric nurse, warned that, given the potential impact of "very, very dangerous" plans, the service's initials may stand for Not Here Soon and the care of the most vulnerable, especially the elderly, would suffer as a result.

Only Lord Owen, the crossbench peer who has been one of the bill's leading critics in the House of Lords, came close to suggesting that, with the legislation close to gaining parliamentary approval, their fight may not succeed. Initially the crowd cheered him. Do David Cameron and Nick Clegg have a mandate for introducing the bill, given the Conservative leader ruled out reorganising the NHS during the 2010 election? No, they bellowed back.

"It's a constitutional outrage that this bill should be presented in this way," said Owen, a former hospital doctor whose father was a GP. Its purpose, he said, "is to commercialise and privatise healthcare".

When he apologised for the failure by him and his fellow peers to make "any fundamental changes" to the bill during its long scrutiny in the Lords, there were boos and cries of "shame". It was heresy to many, but painful reality for others.

Andy Burnham, the shadow health secretary, said Labour would hold a Commons debate and vote on dropping the bill next Tuesday, adding that if he became health secretary he would repeal it.

But privately even some of the speakers at the event accepted that, barring an unlikely major revolt by Liberal Democrat members at their spring conference this weekend, the NHS plans will soon pass through the Lords, and then the Commons again, and then gain the royal assent that campaigners dread.

Before the rally, the BMA's consultants conference had passed a motion of no confidence in Lansley. A Department of Health spokesman said: "The BMA's opposition to the plans on NHS reform and pensions are well-known.

"But doctors on the front line are getting on improving care for patients – across the country patients are being treated in more convenient places and pressure on hospitals is reducing."