More than 5,000 Croydon homes are at risk of flooding, according to the Environment Agency.
Some 5,129 of the borough's homes are at threat from swollen rivers, with 125 of those categorised as high risk.
The figures were published this morning by the London Assembly as the battle to protect homes in Purley, Kenley and Whyteleafe from water continued and ahead of a predicted severe storm tomorrow.
The agency classifies threatened homes as high-risk if there is a greater than one in 30 chance of them flooding.
There are 4,080 Croydon homes at medium risk - standing a less than one in 30 but more than on per cent chance of flooding - and a further 925 at low risk.
Low-risk homes stand a less than one per cent but greater than 0.1 per cent chance of flooding in any given year.
Murad Qureshi, chair of the assembly's environment committee, said: "The figures we have obtained from the Environment Agency show far too many homes in London remain at high flood risk.
"The Prime Minister has said that money is no object, so it’s time for the Mayor to cash in that promise and secure the funding necessary to protect those London homes.
"Current flood defence proposals will only protect a fraction of the homes at high risk."
The statistics were released at the borough braces itself for a severe storm tomorrow.
The Met Office has issued a yellow warning, advising people to wary of possible further flooding in London.
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