Half of the 5,000 complaints made to the Dental Complaints Service were rejected – because they were about the NHS.

NHS patients who are dissatisfied with their dental care must first complain to their local primary care trust (if they cannot resolve the matter with their dentist). If they fail to get satisfaction there, they can complain to the Healthcare Commission, the independent inspectorate.

The commission looked at 16,000 complaints about all aspects of the NHS, and found that most – 30 per cent – of those about dentists concerned fees and charges. "Many patients were concerned about the cost of treatment and the way in which fees were set by practitioners. Some believed they were being treated on the NHS but found they were charged privately," its report said.

The report was conducted before the new dental contract, introduced in April 2006, swept away the old payment system based on 400 separate fees for individual items of treatment and replaced it with three payment bands – £15.90 for a check-up and x-ray, £43.60 for one to six fillings, and £194 for crowns, bridges and more complex work. The commission said these changes "may help make the fees clearer".

More serious complaints, about a dentist's fitness to practise, are dealt with by the General Dental Council, which has the power to strike a dentist off the register.

Mark Hunter, the Liberal Democrat MP for Cheadle, called for a parliamentary debate on the issue. He said: "My constituents and I have been aware of this crisis in NHS dentistry for a considerable time.

"I constantly receive letters not only about the cost of treatment, but also about the difficulty of finding an NHS dentist.

"The rising cost of dental care is only making matters worse. If people can't get to see their dentist for a check-up, then when they do get to see them any problems they might have had are likely to be more severe and therefore cost more to put right. The extraordinary cost of these treatments just adds insult to injury."