A government scheme to make home insurance affordable for families in areas at risk of flooding is wasting householders’ money, advisers say.
It subsidises insurance premiums for homes on flood plains through a £180m tax on everyone else’s home insurance.
But the Committee on Climate Change (CCC) says the costs of the scheme are three times greater than its benefits.
The Department for Environment, Food and Rural Affairs said Flood Re made insurance available and affordable.
The CCC, an independent body set up to advise the government, is calling for the tax on everyone's premiums to be reduced.
In addition, cash should help prevent flood damage rather than be paid to people to clean up after a flood, it says.
It also argues the scheme is too generous.
About half a million homes will have their insurance capped under the plan, but the committee says the insurance industry calculates that only 200,000 of these recipients would genuinely struggle to afford insurance without the support.
It says the cost of the scheme, known as Flood Re, breaks normal government spending rules because it offers negative value for money.
The chair of the CCC’s adaptation sub-committee, Sir John Krebs, said: “Flood Re is set to subsidise many hundreds of thousands of households more than the estimated number that might struggle to afford cover in the free market.
"This makes Flood Re needlessly expensive.”
He called for the scheme to be slimmed down and its emphasis changed.
"Managing flood risk will always be the best way of securing affordable insurance in the long term," he said.
He told BBC News: "A transition should be achieved by helping high-risk homes become more resilient.
“There is a risk that Flood Re will be counter-productive to the long-term management of flood risk in the UK, as it largely removes the financial incentive for households to take steps to avoid being flooded.
"As a consequence, the industry levy funding the scheme could spiral.”
Lord Krebs urged the managers of Flood Re to make it clear to householders that if they were flooded they must restore their home to a more resilient state.
Flood Re was set up in June 2013 by ministers in collaboration with the Association of British Insurers (ABI).
It was designed to be not-for-profit but the CCC says in fact insurers benefit from it because their own risk has been reduced.
The Environment Agency estimates more homes will be at risk from floods in coming decades.
The CCC says Flood Re should be building awareness because many householders in high-risk homes have no idea they are living on a flood plain.
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