London's mayor Sadiq Khan will launch an inquiry into foreign ownership of property in the British capital which has helped push up housing costs, the Guardian newspaper cited him as saying on Thursday.

"It's clear we need to better understand the different roles that overseas money plays in London's housing market, the scale of what's going on, and what action we can take to support development and help Londoners find a home," the Guardian quoted Khan as saying.

"That's why we are commissioning the most thorough research on this matter ever undertaken in Britain - the biggest look of its kind at this issue - so we can figure out exactly what can be done."

London property prices rose more than 12 per cent in the 12 months to July after notching up annual gains of around 20 per cent in mid-2014, according to official data.

The mayor's office has no powers over taxation of property in the city.

The Guardian said Khan's inquiry would focus on the scale and impact of different types of overseas investment in London and consider how other major cities around the world are tackling the problem.

"We welcome investment from around the world in building new homes, including those for first-time buyers," he told the newspaper. "At the same time, as more and more Londoners struggle to get on the property ladder, there are real concerns about the prospect of a surge in the number of homes being bought by overseas investors."

Real estate firm Savills estimated in 2014 that overseas purchases of property in London for investment purposes - rather than foreign residents buying a home in which to live - accounted for around seven per cent of all residential transactions in London.

Khan said there was an urgent need for more transparency in foreign investment. "Londoners need reassuring that dirty money isn't flooding into our property market, and ministers must now make all property ownership in London transparent so we can see exactly who owns what," he said.

Last year, anti-corruption campaign group Transparency International said nearly 200 million pounds ($260 million) of money believed to be the proceeds of foreign corruption had been spent on British properties since 2004 and that amount was probably just the tip of the iceberg. – Reuters