The powerful Public Accounts Committee says a new system of charges announced last week by Rosie Winterton, the Health minister, could provide "incentives" for patients to go private. Ms Winterton announced that 400 separate charges will be replaced by a simpler system of three bands: £15 for check-ups and preventive work such as scaling and polishing; £41 for simple procedures such as fillings and extractions, and £183 for complex work such as crowns or a bridge.

She hailed the new charges as "fairer for patients". But the committee said: "The charging system will need to avoid creating incentives to offer private treatment to registered NHS patients at a lower cost than the NHS charge." And it warned Ms Winterton her department would have to manage risks from doubts among Britain's 26,000 dentists about the new reforms "to prevent an exodus from the NHS at the 11th hour".

The British Dental Association, the professional body representing 18,000 dentists, confirmed patients could be better off opting for private treatment. A senior BDA source said a patient requiring a filling could be better off if they opted for a £15 check-up charge on the NHS then went for private treatment under the same dentist, paying for £30 to £35 for a white filling rather than an amalgam one. "They may be £5 out of pocket but they will get what they want," the source said. "There is the potential for more patients to go private. It depends on how much work they have done."

The committee said two million adults still found it difficult to register with a dentist on the NHS.