Labour leader Ed Miliband today branded the Government's controversial health reforms "extremely dangerous" as he called on the Prime Minister to think again about his "reckless" proposals.
Amid mounting speculation of an imminent announcement that the plans are to be watered down, Mr Miliband warned that the NHS - the "jewel in Britain's crown" - was at risk.
He said in a speech in London that changes had to be made in the running of the NHS - but not the way the Government was planning.
In a hard-hitting attack on the coalition, he described Health Secretary Andrew Lansley's plans as "chaotic" and warned they would make hospital closures more likely.
Mr Miliband called on the Prime Minister to abandon the Bill going through Parliament, pledging that Labour would view any different proposals with an "open mind".
But he warned the current plans were sending the NHS in the wrong direction and made the closure of hospitals more likely.
"The jewel in the British crown is being put at risk. It will send the NHS in the wrong direction in terms of patient care."
The Labour leader said he was concerned that waiting times were already increasing and that GPs would have even less time to deal with patients because of the extra work they would have.
Mr Miliband said Labour's record on the NHS while in Government was "excellent", but he added that changes should continue to be made, such as considering reducing the number of targets.
The attack comes as Mr Cameron and Nick Clegg prepare to launch a "listening exercise" later this week in a bid to reassure critics of the shake-up, which will see GPs handed control of commissioning services.
GPs are expected to form into consortia to take over control of 80% of the NHS budget by 2013, however it is believed this deadline may be formally extended.
It has already been stated that private companies will be prevented from "cherry picking" profitable NHS services.
The Bill's wording is likely to be changed from "any willing provider" of NHS services to "any qualified provider", meaning all providers would have to meet a set of standards. Nevertheless, changing this wording would not alter any of the Bill's provisions for allowing more private companies into the health service.
Mr Miliband said change was "essential", continuing: "The new pressures on the NHS are too great, the new challenges too large for us to think that preserving the status quo will be enough.
"The choice for the NHS is not as the Prime Minister suggests, between change or no change. It's a choice about what that change should be.
"In the 1990s, the government was embarrassed about the state of the NHS, but the citizen had no set of standards to call upon.
"People were abandoned for hours on hospital trolleys, while others sat for an entire night in A&E, and some were asked to wait for weeks for a GP appointment.
"This was partly about investment but not only about it. The NHS today is more accountable to patients at every level
"There is considerable confusion, not least within the Government itself, about why Mr Cameron has embarked on this costly reorganisation of the NHS at a time when funding is so tight.
"What is clear is that the overall intention is to shift significantly the NHS towards what can only be described as a free-market model of healthcare provision, albeit one without an extension of charging."
Liberal Democrat peer Baroness Williams warned that there were would be "very serious" consequences for the coalition unless there were significant changes to the Bill.
"I have a very great desire to see the coalition succeed, I think it's necessary to deal with the really serious crisis facing the country," she told BBC Radio 4's The World At One.
"But I believe unless there are major changes in the health proposals it will be in very great trouble."
Lib Dem opponents of the reforms today published a series of demands which they said were necessary to make the plans comply with party policy.
Evan Harris, one of the leaders of the health revolt at the Lib Dem spring conference and a vice chair of the party's national policy committee, said: "This list of amendments is the minimum needed to satisfy the requirements of Lib Dem policy as set out on the Coalition Agreement and the recent motion, and this will be an essential guide to Lib Dem MPs, the leadership of the party and indeed the Conservatives of what needs to change.
"The Liberal Democrats do not expect their MPs to vote down the Bill, but will not accept our parliamentarians being whipped to vote against any of the necessary amendments needed to provide democratic accountability of GP-led commissioning, guarantee the comprehensive nature of the NHS and rein in the original plans for an NHS market.
"Lib Dem activists and members are encouraged that Nick Clegg and senior figures seem keen to assure us that the NHS reforms will be significantly amended as required by the party, but the Conservatives need to understand that the problem will only be solved if the required changes are fully delivered."
Mr Miliband said that when Labour came to power in 1997, it inherited an NHS in "dire straits", adding: "It was an institution that was profoundly valued, but it was also seen as being in steady and, according to some, irreversible decline. Yet investment and reform transformed the service.
"The NHS is now benefiting from the highest satisfaction ratings it has ever achieved, 72%, against the lowest ever in the 1990s."
The Labour leader said the shift towards free-market healthcare would not help the NHS prepare for the challenges it will face in the future.
"An ageing population and rising chronic disease both demand an NHS which can prevent and intervene earlier. Given these challenges the big task for the NHS is to get family doctors and hospitals working more closely together, but the Government's plans risk setting GP against hospitals in the battle for profits and patients.
"Labour did use the private sector to deliver services for NHS patients, but these proposals take us into a whole different arena, with the prospect of private sector companies being used to carry out commissioning on behalf of GPs."
Michael Fallon, deputy chairman of the Conservative Party, said: "The NHS is too important to be used by Ed Miliband as a political football.
"Ed Miliband claims he supports the NHS but still won't say whether Labour would match our increased investment or cut the NHS in England like they are doing in Wales .
"We want to modernise the NHS so that it is protected for future generations but his plan to scrap the Bill would mean keeping bloated bureaucracies at the expense of patient care.
"Labour's approach of spending less and doing nothing would leave the NHS in crisis."