One in six homes is at risk of flooding in England, the Environment Agency has warned.

And £20bn needs to be invested in flood defences to protect properties in the next 25 years with climate change likely to bring rising sea levels and more rainstorms, the agency said.

Some 5.2 million properties are already at risk of flooding, with 2.4 million threatened by rivers and the sea, and a further 2.8 million at risk from surface water flooding from overflowing drains.

Thousands of health centres and doctors' surgeries, schools and miles of railways and roads are also at risk, according to the agency's Flooding in England report.

Almost half a million homes, offices, factories and warehouses are at a significant risk of flooding from rivers or sea - which means they have a greater than one in 75 chance of being flooded in any year.

The highest number of properties at significant risk are in the South East of England, where some 111,356 are threatened with flooding. Boston, Lincolnshire, has the greatest number of properties at high risk - 23,700 - of any local authority.

Without an increase in investment in flood defences an extra 350,000 properties, including 280,000 more homes, will face a significant risk of flooding by 2035, the EA said. Funding for maintaining and constructing defences will need to double from £570 million in 2010-2011 to more than £1 billion in 2035 to safeguard the same number of properties as are currently protected, the Environment Agency said.

Some £150 million a year will be needed just to address the risk of surface water flooding, which caused many of the problems in the 2007 floods, the agency said.

As the floods, which hit parts of Yorkshire, the Midlands and the South West of England, showed flooding can have a devastating impact on people's lives. In the events two years ago, 13 people died as well as two premature twins, while 55,000 properties were flooded and thousands had to be rescued from the flood waters.

Without increasing funding for defences, the annual cost of damage to residential and commercial properties could rise from £1 billion to £1.6 billion, the agency warned as it released its long term investment strategy for England.

The Environment Agency's chairman Lord Chris Smith said: "The latest climate change data shows that the risk of flooding and coastal erosion will continue to increase in the future due to rising sea levels and more frequent and heavy storms. There are important decisions for us all to take about how to manage these risks to protect people, communities, businesses and the economy in future.