Alan Johnson, the health secretary, alarmed health unions yesterday by opening up a new market for the management of NHS services worth up to £70bn.
He approved a list of 14 private companies that would be available to help primary care trusts in England evaluate the health needs of local people and buy appropriate services. If the trials succeed, the companies may influence the commissioning of services ranging from family planning to chiropody.
The firms include four big US healthcare corporations: Aetna, Humana, Health Dialog Services and UnitedHealth, the Minneapolis-based company whose European division is headed by Tony Blair's former senior health adviser.
The Department of Health said the companies would offer trusts "a bank of specialist expertise". They would be able to analyse data identifying local health problems and negotiate cost-effective contracts with NHS and private sector providers. The trusts control most of the NHS's £90bn annual budget.
The proposal first emerged last year when the department's commercial directorate advertised in the EU's official journal inviting companies to bid to take over the purchase of healthcare for millions of NHS patients. It said the companies might also take over district nursing and other services provided by the PCTs.
Lord Warner, then health minister, withdrew the advertisement after being asked by the Guardian about its political implications. He said there had been "a drafting error."
The scheme approved by Mr Johnson yesterday is a watered-down version which would deny the companies any role in running the services they help to commission. But they are likely to gain influence over decisions about which treatments to ration and which hospitals to close.
Ivan Lewis, the health minister, said: "It will be up to PCTs to decide if they want to use [these] suppliers and, if they choose to do so, PCTs will remain fully responsible and accountable for managing the services provided."
But Unison, the public service union, said the private sector did not have the skills needed to commission healthcare for vulnerable groups of people. Mike Jackson, its senior national officer, said: "We have yet to see proof of the track record of these companies in commissioning on such a broad scale. We fear that patients may be the ones who suffer as a result of this lack of experience."
Hamish Meldrum, chairman of the British Medical Association, said it welcomed the government's decision to withdraw its original plan. The scheme announced yesterday was more cautious, involving local trials.