Insurers are facing a £500 million bill from the extreme autumn and winter weather - putting it on par with the big freeze of 2010, according to professional services firm Deloitte.
Claims have continued to mount after around 1,300 properties were flooded in the run-up to the New Year at an average cost of £30,000 to £40,000. A further 270 flooded properties have been reported last weekend alone.
Deloitte insurance partner James Rakow said: "The flood and storms that we have witnessed since the St Jude storm in October last year threaten to seriously dent the profits made by insurers for the year as a whole, potentially forcing many to recoup costs by raising property insurance premiums."
The Association of British Insurers (ABI), which had pencilled in £426 million worth of claims from storms and flooding over the Christmas and New Year period, said it was too early to say whether the ongoing deluge will result in higher premiums, but added that the industry is geared up for dealing with claims of this magnitude.
A spokesman said: "It will take weeks or months for some of these badly flooded properties to fully dry out and repairs to commence, so we won't know the full cost for a little while yet."
The Environment Agency has issued 14 severe flood warnings along the river, from Datchet to Shepperton Green, including Ham Court and Chertsey.
The ABI is working with the Government to develop a not-for-profit scheme dubbed Flood Re to ensure flood insurance remains widely affordable and available. Current proposals would see Flood Re funded by premiums for properties at high flood risk, which will be capped at £210-£540 depending on the council tax band.
It will be supported by a £180 million annual levy paid by insurers, fixed for five years unless a top up is needed to cover a shortfall in the scheme.
Mr Rakow said the move should keep premiums affordable for high flood risk areas if it is launched in 2015.
Deloitte estimates the premiums and levies going into the scheme will be between £300 million and £400 million for each of the five years. However, if flood claims accelerate, or more areas become classified as high risk, this could potentially double in five to 10 years.