England's ability to sustain current levels of flood protection for homes and businesses faces "major risks", MPs have warned.
Some five million properties across the country, or around one in six, are at risk of flooding from coastal, river and surface water, and climate change is increasing the risks of extreme weather and floods, a report by the Public Accounts Committee said.
While the budget for spending on new defences has been agreed for the next six years, allowing longer term planning, funding for maintenance is only settled annually.
This prevents the Environment Agency from taking a long-term approach on maintaining existing flood protection and secure savings on its spending, the MPs said and urged the Treasury to agree longer budgets for maintenance spending.
The Environment Agency, which is responsible for just under half of all flood defences in the country, has limited resources and must make difficult decisions, but cutting spending on maintaining some flood defences may prove to be a "false economy".
Reducing maintenance could mean new investment in defences is needed sooner than expected, the committee said.
It also warned there was a lack of transparency about the consequences of letting some flood defences fail, with the Environment Agency deciding to stop or reduce funding for maintenance, or handing responsibility over to local communities.
The agency needs to be clearer with communities on the reasons behind changes to looking after defences and what the implications could be for the local area, the report urged.
The MPs also warned that the approach to accessing funding for flood defences from local authorities and businesses was not matching up to the Government's ambition for raising money from outside sources.
There was also a lack of public awareness on the realities of flood risk management, such as responsibilities on landowners to maintain defences, the MPs said, and called on the Environment Agency to make sure the issues are more clearly understood.
Committee member Richard Bacon said: "The Department for Environment, Food and Rural Affairs and the Environment Agency have done a good job in improving the cost-effectiveness of their approach to flood risk management.
"However, there are major risks to the sustainability of current levels of flood protection, which could impact on long term value for money."
A spokesman for the Environment Department (Defra) said: " We thank the Public Accounts Committee for their time and deliberations. Their report raises a number of issues which we will consider carefully.
"However, it should be noted we have spent half a billion pounds more on maintaining and improving flood defences over this Parliament, compared to the previous five years and we will also be investing a record £2.3 billion in new flood defences over the next six years.
"This will make 300,000 homes safer and reduce the risk of floods by 5%."