Thousands of patients have enjoyed free private healthcare thanks to the government's patient "choice" agenda.
Bob Ricketts, Director of System Management at the Department of Health, said 100,000 people have chosen to use private services funded by the NHS since the option was launched in April 2008.
The figures showed that initially there were 2,100 NHS patients a month using the private sector, but this had risen to 8,400 by August 2009.
An increasing number of NHS patients were also opting to use independent-sector treatment centres.
The private sector had been struggling due to the tough economic climate, but the government scheme has now created a business which is said to be worth £200m a year. NHS work also provides 20% of the revenue for a number of private hospitals.
Mr Ricketts announced the figures at a conference ran by analysts Laing and Buisson.
William Laing, Chief Executive of Laing and Buisson, told The Financial Times that it was "great news" for private hospital groups, which could pick and choose NHS patients when they needed the money.
"If and when self-pay revives, they can run down their NHS work," he said.