It's long been known that overseas wealth has played a leading part in driving up London property prices - at the top end if not throughout.

But it's now alleged that much of the foreign wealth pouring into expensive homes in the capital is dirty: the proceeds of crime.

A leading crime-fighter has warned that foreign criminals are laundering billions of pounds by purchasing prime London property.

Up for grabs: Are prime central London property prices being inflated by dirty money?

Donald Toon of the National Crime Agency has said he is alarmed by the number of homes registered to complex offshore corporations - some of which have been bought with laundered money.

He added that the inflows are big enough to be responsible for driving London property prices artificially high.

The Treasury has received a £150million windfall in the past three months from a tax on properties purchased by companies, trusts and investment funds, rather than individuals, supporting Mr Toon's claim.

When the tax was first in operation in 2013/14, it raised £100million from 3,990 houses.

Mr Toon told The Times: 'I believe the London property market has been skewed by laundered money. Prices are being artificially driven up by overseas criminals who want to sequester their assets here in the UK.'

Hundreds of billions of pounds are laundered in the City every year, according to the National Crime Agency, and investigations are intensifying into the matter.

Mr Toon added: 'Prices of high end property are being artificially driven up by the desire of overseas criminals to sequester their assets here in the UK. What they are doing is distorting the market.

Flying in: Overseas buyers have always stood accused of bidding up London property - but now it's feared a lot of the money is the proceeds of crime.

'If they (estate agents) have a suspicion that there may be money laundering involved then they absolutely should be submitting a suspicious activity report.

'You are at risk of committing a criminal offence if you do not do that.'

Foreign millionaires have long stood accused of driving up London house prices.

While they may be targeting multimillion-pound central London properties, buyers who are squeezed out of that market then look elsewhere and in turn bid up prices in slightly less expensive areas.