Finding an NHS dentist could become even harder as a radical overhaul of dental charges to take effect next week has angered dentists who are threatening to leave the NHS.

A survey of 45 local dental committee chairmen in England, of whom 23 responded, found that almost all (96 per cent) believe they are likely to see fewer NHS patients because of the reforms.

The survey was carried out for ITV1's Tonight With Trevor McDonald, to be broadcast this evening.

A separate survey of local committees by the British Dental Association found 90 per cent of the 35 committees that responded predicted access to NHS dentistry would worsen. All 109 committees in England and Wales were contacted for the survey. The Department of Health said the surveys were unrepresentative and claimed most dentists were signing new contracts. But the British Dental Association (BDA) said two-thirds of those who had signed had done so "in dispute".

A spokeswoman for the BDA said: "The Health Department have not negotiated anything. Around 90 per cent of dentists will probably sign because if they don't they can't work in the NHS but they will then move into the dispute process."

The cause of the dentists' displeasure is a new charging system under which the current 400 separate payments will be simplified into three price bands. The lowest NHS charge will be £15 for an examination and report, a near £10 increase, but the highest charge will be £189, around £200 less than the current top charge. The middle band charge of £40 will cover one to six fillings, previously priced at £10 to £12 each.

The new system is designed to be simpler and fairer but has been criticised by dentists who claim it leaves little time for preventative work and is confusing. Instead of being paid for each treatment they carry out, dentists will be given a guaranteed income based on previous workload, about £80,000 a year for three years.

Dr Nick Patsias, the chairman of the London Dental Committee, told Tonight With Trevor McDonald: "The new vocational trainees that are coming in, they want to go into private dentistry almost immediately because they don't see a future in NHS dentistry any more."

Rosie Winterton, a Health minister, said: "If dentists choose not to sign up, the local NHS will use that funding to buy services from other dentists."