The public has just 13 days to halt the government’s controversial health reforms and save the NHS from falling into the hands of private companies, a union leader has warned.

Len McCluskey, general secretary of Unite, accused ministers of “steamrollering” its Health and Social care Bill through against widespread opposition from health professionals.

He joined thousands of nurses, midwives, doctors, physiotherapists, cleaners, porters and other NHS workers at a rally in Westminster in a last-ditch attempt to scupper the Bill.

The protest was held a day after opposition efforts to rein in the bill were defeated in the House of Lords.

Peers voted down amendments designed to restrict the role of regulator Monitor and protect the NHS from European competition law, in a sign that concessions made by Andrew Lansley may have been enough to reassure Liberal Democrat critics and secure the passage of the Bill through Parliament by the May 9 Queen’s Speech.

Mr McCluskey told the rally it was expected that the bill will pass into law by 20 March, despite “almost universal opposition” from health professionals, from doctors to paramedics, as well as the general public.

“We have just 13 days to save the NHS from falling into the hands of the private healthcare companies that are set to make millions in profits for their shareholders.

Dave Prentis, Unison’s general secretary, said: “This is our last chance to save the NHS. Cameron knows he can’t allow the Bill to hang around any longer because the more people see of it, the more they hate it. The more people read it, the more come out in their droves and demand it is scrapped.

“Cameron is forcing it through. A few cosmetic tweaks from Clegg and that’s it - no more debates, no further chance for MPs to have any meaningful say. They blocked disclosure of the risk register, they blocked a debate on the e-petition that more than 160,000 of us signed. Now they want to rush the Bill onto the statute book before the Budget.”

British Medical Association chairman Dr Hamish Meldrum said the government’s reforms would “splinter, fragment and undermine” the NHS.

“We have never said the NHS must not change - but not at this time and not with this bill.”

Dr Peter Carter, leader of the Royal College of Nursing, warned there would be another reorganisation of the NHS within four years to “clear up the mess” caused by the bill.