GPs and Labour MPs have warned that NHS reforms due to take effect in the coming weeks will lead to a free-for-all for private providers.
In particular, new guidelines known as Section 75 - already revised under intense political pressure - are causing concern because they say that the award of a new contract without a competition can only happen:
...where the relevant body is satisfied that the services to which the contract relates are capable of being provided only by that provider.
Critics say that in practise the phrasing means that new proposals can virtually never be given the go-ahead without competition from private providers.
"That isn't the NHS that we've had for 65 years," says Labour's shadow health secretary Andy Burnham.
"There is huge disquiet across the medical profession about these regulations and the thought that they are going to be instructed to open every contract to full market testing."
Along with her colleagues, Hackney GP Dr Deborah Colvin had offered to run their own out-of-hours service.
Expecting their plans to be welcomed with open arms, they were instead turned down by commissioning authorities who said they could not be considered unless they were prepared to tender competitvely.
Dr Colvin said such a process would be "incredibly expensive and complicated," estimating a cost of up to £50,000.
"I think it's going to happen right across the country, over and over again," she warned.
But health secretary Jeremy Hunt rejected the assertion that competition would be given a free reign in a new-look NHS.
"There is no free-for-all, because the decisions are being taken by local doctors - and I think it's a very exciting thing for the NHS," he said. "We're already seeing some big improvements."
Independent experts say that the rules are still vague.
"The new regulations have created more uncertainty, not less. It all depends on how the lawyers interpret what the government means," says Professor Chris Ham, chief executive of the King's Fund.
"What that means is GPs will be working in the dark until the lawyers have made their interpretation. There is a lot of uncertainty out there at the moment."
Under the coalition's NHS reforms, groups of GPs begin to take control of spending and commissioning decisions from April 1st.
With just days to go until that point, concerns about the involvement of competition and private sector provision are very much alive.