The British Medical Association (BMA) has warned that the NHS cannot afford to keep using the private sector.
It said that it was important not to "waste" money on private firms, given the economic climate.
The "Look After our NHS" campaign has been running since last year, but it has been aimed mainly at doctors. The BMA now plans to broaden the campaign out to members of the public, and is asking patients to sign up.
According to figures published by the BMA, hospitals built under private finance initiatives are costing the health service six times their worth.
BMA chairman Dr Hamish Meldrum said: "As the public purse strings tighten, it is crucial that public money is no longer wasted on expensive commercial experiments."
Critics have questioned the timing of this campaign, as the private sector is now getting less business from the NHS.
