The coalition government's proposed reforms of the NHS in England were defended by the British Prime Minister David Cameron even as lawmakers began their first debate on the bill.
Amid increasing criticism from health unions, the Conservative leader rejected claims that the reforms would amount to privatisation of the service, free at the point of delivery since its founding in 1948.
Under the plans, family doctors will be responsible for buying in patient care from 2013, with a new NHS commissioning board overseeing the process.
"There is no privatisation taking place, the NHS will be just like you experience it now - it is free at the point of use, you don't pay anything, and it is according to your need," Cameron said.
"But I think it is a good thing if patients and their GPs are able to choose between different providers.
"Of course, some of the trade unions are nervous about this because it will mean greater choices for GPs and patients.
"It will mean that, for instance, they will be able to choose between hospitals and between services and sometimes trade unions don't like that sort of choice."
The changes would see GPs form consortia which will take control of 80 percent of the NHS budget, buying services from providers in the public, private and voluntary sectors.
The government argues that the plans will improve patient care and efficiency, as well as saving the NHS £1.7 billion a year.
The 280-clause Health and Social Care Bill would abolish all of England's 152 primary care trusts (PCTs), which currently plan services and decide how money should be spent.
"This bill is heading for trouble," said Dave Prentis, general secretary of the public sector union Unison.
"This titanic reorganisation threatens to sink the NHS. The government should step back from the brink and pronounce this Bill DOA - dead on arrival."
"The fact is there is very little support for this bill from anywhere.
"Many GPs are opposed to it, as are patients, NHS staff, clinicians, charities, think tanks, MPs and unions.
"The government's vanity project is undemocratic, unaffordable and unnecessary."
A recent YouGov survey revealed that only one in four people supports doctors using private companies to provide NHS services.
The survey of almost 2,000 adults for Unison showed that half were opposed to the move, including 56% of Liberal Democrat party voters.
Only 46% of Conservative party voters supported private firms providing NHS services, with 22% registering a "don't know" response.
The study also showed that half of those surveyed were against GPs employing private management groups.
Health workers from up and down the country are expected to congregate outside parliament later Monday, carrying estate agent signs bearing the message "NHS, Not for Sale".