Consumers may be overpaying for dental care because some dentists with both NHS and private arms push patients down the more expensive private route.
The Office of Fair Trading (OFT) says this is sometimes due to a lack of knowledge, but sometimes it is deliberate.
It today calls for greater patient choice and more competition in the dentistry market, following an investigation.
The regulator's study found each year around 500,000 patients may be provided with inaccurate information which puts them at risk of overpaying.
Other issues highlighted in the investigation include the complexity of the complaints process and pressure selling by dentists of payment plans, which are similar to insurance.
On complaints, the OFT says there are too many hoops to jump through for both dentists and consumers.
John Fingleton, OFT chief executive, says: "Our study has raised significant concerns about the UK dentistry market which need to be tackled quickly in the interest of patients.
"We also unearthed evidence some patients may be receiving deliberately inaccurate information about their entitlement to NHS dental treatment, and we expect to see robust action taken against such potential misconduct by dentists."
Lack of competition
Concerns were also voiced about current NHS dental contracts in England. As the majority are rolling with no end date, it means new contracts only tend to be issued if there's a shortfall in the existing supply of NHS dental treatment, or if a dentist with an existing contract gives it up.
This means it's difficult for new dental practices to be established, restricting competition.
The report also raises concerns patients are being restricted from directly accessing dental care professionals, such as hygienists, without a referral from a dentist, which the OFT considers unjustified.
The OFT has identified a number of recommendations to address these concerns, which include:
- Calling on NHS commissioning bodies, the General Dental Council and the Care Quality Commission to be proactive in enforcing rules that require dentists to provide clear and accurate information about prices and treatments.
- Calling for the current complaints system to be made simpler.
- Urging the General Dental Council to remove restrictions preventing patients making appointments to see hygienists, dental therapists and clinical dental technicians directly.
- Urging the Department of Health to redesign NHS dental contracts to make them easier for practices to enter the market and expand.
These are recommendations so do not constitute enforcement action.
Following discussions with the OFT, the British Dental Association has agreed to develop a code of practice covering the sale of dental payment plans.