Health professionals and patients fear NHS reforms will "destroy essential services", the senior doctor leading an urgent review of the controversial government plans has warned.
Professor Steve Field detailed a number of concerns surrounding the radical shake-up in an interview with The Guardian, mostly surrounding a push to increase competition within the health service.
He insisted that the expert panel examining the need for changes to the Health and Social Care Bill, due to report to ministers within weeks, had not reached its final conclusions and that he was simply reflecting concerns raised during a "listening exercise" ordered last month amid a welter of political and medical clamour against the reforms.
But his words are certain to highlight the scale of revision that is likely to be required if Health Secretary Andrew Lansley's project is to survive mounting dissent. Ministers have promised "substantial" changes after calling a "pause" to the progress of the Bill.
Deputy Prime Minister Nick Clegg has vowed to veto the legislation - elements of which are deeply unpopular among Liberal Democrat MPs and activists - as part of efforts to demonstrate a greater influence by his party in the Tory-led coalition Government following disastrous results at the ballot box last week.
The blueprint would scrap primary care trusts and strategic health authorities and give GP groups control of around £80 billion worth of NHS spending, with a remit to commission treatment and services from "any willing provider" - including private companies. It also places a duty of watchdog Monitor to promote competition in the provision of health services.
Accusations that the Government was effectively seeking to privatise the NHS have been among the most politically damaging to the coalition.
In the comments reported by The Guardian, Prof Field, who chairs the NHS Future Forum, said: "If you had a free market, that would destroy essential services in very big hospitals but also might destroy the services that need to be provided in small hospitals. The risk in going forward (with the Bill) as it is, is (of) destabilising the NHS at a local level. It would lead to some hospitals not being able to continue as they are," he added.
Shadow health secretary John Healey said: "From the start, Labour has led the opposition to the Health Bill and argued against setting up the NHS as a free market, regulated in the same way as the energy industry.
"The legislation as it stands will break up the health service and open up all NHS services to private companies."