Dentists in Kingston are facing large financial penalties after collectively falling nearly £500,000 behind in their contracts for not treating enough NHS patients.

Out of the 25 NHS dentists in the borough, 16 were facing “claw back” and one was facing a repayment of £50,000 or more as recently as March, according to figures obtained from the borough’s NHS by a private dental company.

Kingston Primary Care Trust (PCT) denied claims it was “one of the worst performing areas in the country” and said the situation had improved since they released the information.

It also had to backtrack from presenting an even worse scenario, initially saying that 24 out of 25 dentists were underperforming, 19 by more than £50,000, after mis-reading the question sent in by DPAS, a company that provides private dental plans, which then released the figures.

A PCT spokesman said: "It appears that the questions were misread at the time and the numbers in our response refer to the contract values and not on contract underperformance."

A couple of surgeries that needed help have been identified by the PCT but health chiefs will work with surgeries to improve their performance, instead of demanding the money back.

The British Dental Association said clawing the money back could force practices across the country to close.

Kingston Primary Care Trust spokesman said: ”Our approach will be to work with any dental practice not achieving their contracted value with the option to withhold payments until the contract value has been achieved.

“This will avoid the need to ‘claw back’ allocated funding.”

Two years ago dentists moved from a fee-per-item system to one based on locally-agreed contracts between dentists and their PCTs but nationwide about 5m fewer treatments were carried out in 2007-08 than were budgeted for by the health service.

For the year ending March 31, 2008, Kingston Primary Care Trust commissioned 181,697 units of dental activity but only 164,146.10 were delivered.

Quentin Skinner, chairman of DPAS, a company that provides private dental plans which obtained the figures, using the Freedom of Information Act to shed light on the way the new dental contracts were working.

At the moment only 43 percent of the Kingston population have access to an NHS dentist but Kingston PCT wants to increase access to 50 percent next year and 70 percent in coming years.