Britain now has a record number of estate agents, official figures have revealed, underlining fears that the fledgling economic recovery is based on inflating an unsustainable housing bubble.

The number of people employed in "real estate activities" increased by 9.9% between March and June (the latest month for which data are available), according to the Office for National Statistics.

That was the fastest percentage increase in any sector of the economy; and a rise of 77,000 in the number of estate agents over the past year has taken the total number of people employed in the sector to 562,000, the largest number since records began in 1978.

Growing confidence in the outlook for the housing market has been a key component of the economic upturn that led the chancellor, George Osborne, to claim in a speech on Monday that the UK is "turning a corner".

Prices across the country rose by 3.5% in the year to August, according to the Nationwide, with much sharper increases in London and the south east.

However, with the most potent element of Osborne's Help to Buy scheme due to kick in next January, offering taxpayer-backed guarantees on homes worth up to £600,000, news of a jump in the number of estate agents will underline fears that the UK is on its way to another unsustainable housing boom.

"We're no longer a nation of shopkeepers, we're becoming a nation of estate agents," said Danny Gabay, director of economics consultancy Fathom. "I would certainly agree that the economy has turned a corner; my concern is about how sustainable this recovery will be, given that it is based on using government subsidies to encourage already over-extended households to take on even more debt to finance their consumption".

Simon Rubinsohn, chief economist at the Royal Institution of Chartered Surveyors, said any recent increase in jobs among estate agents is likely to have been concentrated in the south, where the housing market upturn is most evident.

"I think it's early days across much of the country. It may be capturing some of the impact from London and the south east, but when I look at the comments from our members elsewhere in the country, I don't sense they're rushing to take on lots of new employees, or open new offices: it's a bit premature."