LONDON (Reuters) - The number of homes changing hands almost halved in June from a year ago, highlighting the difficulties facing homebuilders, retailers and the public finances as a housing market downturn intensifies.

Revenue and Customs said property transactions numbered a seasonally-adjusted 77,000 last month, the lowest since the current series began in April 2005, after a downwardly revised 91,000 in May.

"This is a double-whammy," said George Buckley, chief UK economist at Deutsche Bank. "Not only will weaker transactions weigh on retail sales but there will be a big hit in terms of lost stamp duty revenues."

Total stamp duty raised more than 14 billion pounds in the last fiscal year, according to the latest Budget figures.

House prices have fallen by almost 10 percent from their peak last August as the credit crunch has made it harder and more expensive to get mortgage finance.

The even faster fall in the number of property transactions and mortgage approvals has fuelled concern that the housing market downturn could take the economy down with it.

Construction activity is already falling at its sharpest pace since records began more than a decade ago and house-builders such as Persimmon (PSN.L: Quote, Profile, Research) and Bovis Homes (BVS.L: Quote, Profile, Research) have slashed their workforce.