Eight in 10 of the homes that are at high risk of flooding in England are now in towns and cities, according to analysis by the National Housing Federation (NHF), which said social housing tenants are disproportionately vulnerable to the financial cost.

Research found that 839,000 homes in urban areas are now classed as being at high risk of surface water flooding, a threefold increase since 2018.

Constituencies in Thurrock, Basildon, Bootle, Sefton and Southport had the highest proportion of at-risk homes. Areas of London, including Hackney, Barking and Tottenham, also featured in the top 10, and also had the highest proportion of social housing tenants.

Alistair Smyth, the director of policy and research at the NHF, said: “With surface-water flooding a fast-growing threat in towns and cities, this poses a direct risk to people and families living in social housing.

“Our climate is changing faster than our infrastructure can handle, and social housing residents are more exposed, less protected and least able to absorb the financial shock when floods hit. While housing associations operating in higher risk areas are investing significant time and resource into protecting residents, this is a national risk that needs a national response.”

According to the Environment Agency (EA), a home is considered to be at high risk when it has at least a one in 30 chance of being flooded each year. Extreme rainfall, ageing infrastructure and rapid urbanisation are fuelling the problem.

Surface-water flooding – when rainwater is not dispersed through normal drainage systems or does not soak into the ground – is increasing flooding in urban areas, and the EA forecasts the number of properties at risk is likely to treble over the next 50 years.

The NHF said people who lived in social housing, which is predominantly in urban areas, were disproportionately impacted. In the 10 worst affected urban constituencies in England for flooding, an average of one in four households lived in social housing.

Social tenants are less likely to have contents insurance because of the costs, leaving them more exposed to financial losses from water damage. About one in three of the poorest households in England have contents insurance compared with nine in 10 homeowners.

Tracey Garrett, the chief executive of the National Flood Forum charity, said there needed to be a “step change” in how water was managed in urban areas where drainage systems had become overwhelmed by the effects of climate change.

“Every week we hear from people whose homes have been inundated with filthy water, often containing sewage, and many have been flooded multiple times,” Garrett said, adding there was a growing concern that “those living in rented or social housing, and on lower incomes, are the ones being hit hardest”.

“These households are often located in higher-risk areas but have the least ability to adapt or protect their homes. Many are experiencing repeated flooding, with little clarity on who is responsible for fixing the problem or how long-term solutions will be delivered.

“Often people are afraid to speak out or report flooding due to feeling that doing so may affect their tenancy.”

Ann Hoyles, 64, a social housing tenant, said her bungalow in Warrington was ruined by a flood on New Year’s Day last year. She has health issues, including arthritis, and had spent her life savings renovating the property and garden as she considered it to be her “forever home”.

“I had heard of flooding in that area before but I was told the problem had been sorted. And with social housing you don’t get many options of what you can refuse, so I took it,” she said.

“I lost everything. The water was contaminated so it ruined everything. I’m on crutches so I couldn’t walk out and had to be rescued in a boat. It was a nightmare, I couldn’t sleep as I had no idea where I was going to live.”

Although she could afford contents insurance, she did not have the most comprehensive cover. “I didn’t have a lot of money so I just had to opt for the cheapest one, and it meant I did have a lot of issues when it came to claim,” she said.

Paul Warburton, the director of housing services at Torus housing association which owns her home, said it spent £500,000 dealing with the cost of that flood, only a few years after a previous flood in the same area.

“Half a million pounds – that’s lot of new bathrooms we could have installed, new homes we could’ve built,” he said. “And social housing is a precious commodity, there’s such massive demand.”

He said flooding was becoming one of the biggest financial challenges the organisation faced.

“Properties are costing more to insure, so that’s putting more financial strain on us as an organisation. And what’s not insured is the cost of putting people in a hotel, subsistence, moving people’s furniture out. The last flood took 52 homes out of action for 12 months,” he said.

“We’ve had flood warnings on a number of sites, so every time it rains we dread it. If this keeps happening we’re probably going to end up with about 100 properties that no one wants to live in, and then what do we do with them?”