A "secret shopper" survey published today by the consumer organisation Which? shows that more than half of surgeries are refusing to take on new NHS patients, with only 36 per cent accepting all those seeking NHS treatment.

In Yorkshire the situation is almost critical, with only 15 per cent of surgeries saying they would agree to take on NHS patients. That figure was second only to the North-West, with 13 per cent.

Today's figures suggest little has changed since February 2004, when more than 300 people, including pensioners and pregnant women, queued round the block before dawn in Scarborough in a desperate search for fillings, crowns and a scale and polish because of a lack of NHS dentists who had left for the private sector.

Since then the Yorkshire Post's Stop the Rot campaign has been calling for thousands of patients denied NHS care in the region to be given access to affordable treatment. Today's findings by Which? suggest that is still far from happening.

Although today's national figures do represent an improvement on 2005, when only 31 per cent were taking on all NHS patients, in Yorkshire, the North-West and the South Central region the situation is far more serious.

In some areas of the country, much higher percentages of NHS patients are being accepted – with 63 per cent of surgeries in the West Midlands taking on all patients and 59 per cent in London.

Overall, 11 per cent of dental practices would accept certain patients, usually children and those on benefits or exempt from charges, while three per cent said they would defer a decision until after a check-up.

According to the research, practices in the South Central region and the South-West were most likely to be taking on only certain NHS patients. The results, which looked at 466 dental surgeries across the country, come a year after the start of new NHS dentists' contracts.

Which? health campaigner Frances Blunden said: "As long as the Department of Health continues to allocate money for Primary Care Trusts (PCTs) to spend on dentistry on the basis of previous levels of NHS provision in their area, they will perpetuate the stark inequalities in access.

"Where needs are not currently being met by the NHS, people are either putting off having treatment or are being forced to go private.

"If the Government is serious about creating a patient-centred approach to NHS dentistry, then Primary Care Trust allocations must be related to local needs."

Responding to the report, Health Minister Rosie Winterton said: "It was agreed by all that the old system of NHS dentistry was deeply flawed and had to be modernised. Dentists were drifting away from the NHS – and the old rules meant the money to replace them was lost to the local NHS when they left.

"Thanks to the reforms, PCTs now have the power and money to improve and develop local dental services and are now turning the corner in improving access to dentistry. Which's method of calculating access is deeply flawed, taking no account of existing levels of access. There is clear evidence that the reforms are beginning to improve access across the country."

Shadow health secretary Andrew Lansley said: "The new contract is not serving patients or dentists well. NHS dentistry is costing the NHS considerably more and yet in many parts of the country patients are finding that they cannot get access to it."