The senior doctor leading a review of the government’s controversial health reforms has warned they would destabilise the NHS and undermine key hospital services.
Professor Steve Field said pressing ahead with giving a watchdog a duty to promote competition could “destroy essential services”.
Ministers have promised “substantial” changes to the Health and Social Care Bill after a political and medical outcry which forced a “pause” to the legislation.
The current coalition plans 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.
Prof Field was appointed to chair the NHS Future Forum which was set up to run a “listening exercise” with health professionals to identify what changes were needed.
Accusations that the government was effectively seeking to privatise the NHS have been among the most politically damaging to the coalition.
In direct contrast to the existing plans, Prof Field said, regulator Monitor should be obliged to promote co-operation, collaboration and integration of services.
“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,” he said.
He told the newspaper: “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 - suggesting University Hospital Birmingham would be unable to run its trauma centre for example.
“We need some significant changes in how the role of Monitor is described and enacted in order to reassure patients and doctors and nurses.”
Among initial suggestions made by Prof Field were lists of “designated” services that all hospitals should provide to ensure services were available in all parts of the country.
He also said new GP consortia should include a nurse on their boards - an idea promoted earlier by deputy prime minister Nick Clegg.
Mr Clegg has said he will block the reforms - which are highly unpopular among Liberal Democrats - unless they are significantly altered.
Prof Field said that the reforms were not “clear enough” to the public but also that some senior doctors were guilty of “shroud-waving” and scaring patients over the legislation’s impact.
Mr Clegg, on a visit to a Sheffield hospital, said nurses were the “heart and soul” of the NHS and should be part of the consortiums making the decisions on how money is spent.
He vowed that there would be no “backdoor privatisation” of the NHS.
A Department of Health spokesman said: “We recognise that people have some big questions about how competition in the NHS should work.
“Steve Field is quite right to say we’re looking for changes to make the legislation more clear and effective. We have always been very clear that it is not a free market, it’s a social and a regulated market.
“Competition must be on quality and not on price, enabling commissioners to secure the best quality services for patients.”