Up to 1 million people in England lost their NHS dentist under government reforms introduced this month, it was revealed today.

The government admitted around 2,000 dentists had rejected the controversial new NHS contract. Its figures showed 1,096 contracts were turned down, with 8,323 being signed. Each contract can cover more than one dentist in a practice.

The health minister, Rosie Winterton, claimed the figures showed fears that dentists would leave the NHS in a mass exodus "were unfounded", with nine out of 10 having signed up.

She said contracts signed by dentists accounted for around 96% of NHS dental services, and added that many of those who rejected the contract had a "relatively small NHS commitment".

However, the Conservative health spokesman, Andrew Lansley, said the figures equated to a 4% decline in NHS dental provision and would lead to almost 3m fewer dental treatments being offered.

The statistics confirmed predictions by the British Dental Association that one in 10 dentists would reject the contract, which came into force on April 1.

"This week, almost 2,000 dentists have left the NHS," Susie Sanderson, the chairwoman of the BDA's executive board, said.

"Everybody - patients, dentists, consumer organisations and primary care trusts - knows there is a problem. Why is it only the government that insists everything is fine?"

Ms Winterton admitted 30% of dentists who had signed the new contract were disputing their terms and conditions, although that was half the number predicted by the BDA.

The acting chief dental officer, Dr Barry Cockcroft, added it was "utterly unlikely" that the 30% of contracts in dispute would end up rejected by dentists.

The reforms mean that instead of being paid for each piece of work they do, dentists will receive a "block contract" from their primary care trust. The contract commits them to perform a set number of "units" of treatment per year.

Some dentists say the contract does not give them enough time to see patients or advise them how to protect their teeth, and claim they have been offered far less NHS work than they wanted.

Steve Webb, the Liberal Democrat health spokesman, said the government was "living in cloud cuckoo land" if it thought NHS dentistry was in a good state.

"Their own figures show that hundreds of dentists have pulled out of the NHS because of the new contract," he said. "In addition, many more are cutting their hours or are in dispute over their contract.

"The long-term future of NHS dentistry looks bleak unless the government urgently reviews the new contract."