More than 500 properties in Croydon are owned by companies registered in offshore tax havens, which campaigners warn could be being exploited by criminals.
Analysis of the Land Registry for England and Wales has revealed more than 87,000 properties worth an estimated £100bn are owned by anonymous overseas companies.
Campaign group Global Witness, which carried out the research, says the figures demonstrate the “alarming scale of the UK’s secret property scandal”, which criminals could be using to launder money.
In Croydon, there are 618 properties owned by companies registered outside of the UK.
Of these, 575 are owned by companies based in so-called secrecy jurisdictions, or tax havens – countries whose laws allow them to keep their financial activities private or to pay a low amount of tax.
Companies registered in Jersey own the largest share in Croydon, with 172 properties.
This is followed by the British Virgin Islands, on 143 properties, and the Isle of Man, with 79.
Information about the sale price has been provided for 38% of the tax haven-owned properties, which had a combined cost of £330 million.
Global Witness used the average price of property in Croydon to estimate the value of the remaining properties, which suggests the true value could be £511 million after inflation is taken into account.
This could be a conservative estimate, as property prices in England and Wales generally rise above the rate of inflation, it added.
The group said the government had pledged to introduce a new register of UK property owners, but that progress had been slow.
Ava Lee, senior anti-corruption campaigner at Global Witness, said: “It’s increasingly clear that UK property is one of the favourite tools of the criminal and corrupt for stashing and laundering stolen cash.
“There’s some good news. Parliament is reviewing a draft law that could force these secret owners out of the shadows.
“We’re calling on the Government to table this legislation as quickly as possible, so we can find out who really owns so much of the UK.”
The new legislation would mean companies buying property in the UK would have to reveal the identity of their owners.
Across London, there are 43,270 properties owned by overseas companies, 93% of which are registered in secret jurisdictions – 40,097 in total.
The properties owned by companies registered in tax havens are worth an estimated £73 billion.
HMRC said there is “absolutely no place for illicit finance in the UK”.
“We take our response to money laundering very seriously through our supervision of high risk sectors,” a spokesman said.
“Increasingly we are seeking to use our supervisory, enforcement and tax powers in concert, enabling us to increase our focus on the enablers of tax crime and money laundering.”
He added that estate agents were legally obliged to register with HMRC for anti-money laundering supervision, and faced action if they failed to do so.