Opponents of the government's plans to overhaul the NHS in England have held a rally in Westminster.
Around 2,000 nurses, midwives, doctors, cleaners, porters and other workers and activists attended the event.
TUC general secretary Brendan Barber warned that the Health and Social Care Bill would amount to "privatisation" of health services.
The Department of Health said the plans would "put patients at the heart of the NHS" and "reduce needless bureaucracy".
The bill aims to give GPs control of much of the NHS budget and would open up the health service to greater competition from the private and voluntary sector.
It has had a difficult passage through Parliament, with some Lib Dems in the House of Lords expressing concerns.
But ministers won a series of votes on Tuesday night, which makes it more likely the legislation will pass into law within weeks.
However, protesters are urging the government to drop the bill.
At the protest, in Central Hall, Mr Barber said: "Together we are speaking up for a publicly accountable health service, for the values that make our NHS special and for the ethos of public service itself.
"With the Health and Social Care Bill now going through the Lords, it's vital that we make our voices heard. I want the message to go out loud and clear that our NHS is not for sale, not today, not tomorrow, and not ever."
Mr Barber argued that the bill "represents the biggest threat our NHS has ever seen" and will mean "£3bn spent on change instead of care".
Dave Prentis, general secretary of the public service union Unison, said: "The clock is ticking and we are running out of time to save the NHS. Health workers from across the country will make their opposition to the dangerous Health and Social Care Bill heard loud and clear today in London.
"They know that the bill will mean the end of the NHS as we know it and they want it to be dropped."
Other speakers at the rally include shadow health secretary Andy Burnham and comedian Jo Brand, who once worked as a psychiatric nurse.
A Department of Health spokeswoman said: "The Health and Social Care Bill will hand power to GPs, put patients at the heart of the NHS, and reduce needless bureaucracy.
"The independent NHS Future Forum found broad support for the principles of our plans. And only this week 75 GP leaders, representing thousands of patients, outlined their support for shifting power to the front line.
"Without the bill we couldn't remove two layers of bureaucracy and reinvest £4.5bn in patient care."