The crisis in NHS dentistry is underlined today by a survey showing that more than seven million people in England and Wales have been unable to get an NHS appointment in the past 20 months.

Two thirds opted for private treatment and one third went without treatment, the survey by Citizens Advice Bureaux found.

The results come after The Independent revealed last week that UK dentistry is the most expensive in Europe and dentists are reducing the proportion of their income they earn from the NHS.

The CAB survey, conducted by Ipsos Mori, was based on a poll of 1,800 adults last month. It found 31 per cent of those who had not been to an NHS dentist since April 2006, said they had been unable to find one to treat them, equivalent to 7.4 million people. David Harker, chief executive, said: "These figures show the scale of the lack of access to NHS dentistry. People on low incomes are particularly affected as private treatment for them is just not an option."

The report included cases of people faced with long waits for NHS treatment or long journeys to get to it. One CAB office in North Yorkshire said a pensioner on a low income had been told she needed follow-up care after emergency hospital treatment but found both dental practices in her area had 12-month waiting lists.

Ann Keen, a Health minister, said funding for NHS dentistry had been boosted by 11 per cent next year. "Improving access to NHS dentistry is now a national priority for the health service. We will be holding primary care trusts to account on delivering improvements – patients deserve no less."