Growing pressure to clean up Britain’s rivers to meet bathing water quality is a “game changer” that will require more government funding as the public embrace the outdoors, the head of the Environment Agency has said.

A growing number of river users are calling for action to tackle the routine and legal discharge of untreated sewage into Britain’s waterways, which they say amounts to treating them like an open sewer.

Campaigners in Ilkley, West Yorkshire, have applied for the River Wharfe to be granted bathing water status, which will force Yorkshire Water and the Environment Agency to clean up the river, dramatically reduce or stop sewage discharges, and regularly monitor the water quality.

In the south-east, Theo Thomas, the chief executive of campaign group London Waterkeeper, is aiming to have sections of the Thames designated as bathing water, and in the Cotswolds, the Windrush Against Sewage Pollution (Wasp) campaign is preparing to apply for bathing water status for three areas of the River Windrush where people have swum for decades.

Emma Howard Boyd, chair of the Environment Agency, welcomed what she said was the “public embracing the environment”. “This move to bathing water status is a game changer in terms of moving the dial as to what is expected from water quality,” she said.

“There is a whole process that has to be gone through in terms of numbers [using the rivers] and other requirements, but we went through that programme with bathing waters in the sea. I think this could really move us to the next stage in terms of how we work on the water issue.”

There are 15,700 combined sewerage overflows where the EA permits water companies to discharge untreated sewage into rivers in extreme weather conditions, according to WWF figures. But WWF analysis shows the overflows are discharging sewage far more often than they should be.

Just 14% of rivers are rated as good under the EU water framework directive, which provides a baseline quality for the health of wildlife and habitats in inland waters.

The scale of the pollution that regularly occurs is shrouded in secrecy. Water companies are allowed to monitor their own discharges and do not release real-time data on how often, and for how long, combined sewerage overflows release sewage into any particular river. Campaigners say the permits to discharge are licences to pollute and want the rules changed.

Members of the public are increasingly turning to the water quality test – bathing water status – which is applied to coastal waters to make it clear they are safe to swim in.

Thomas said: “There are hundreds of swimming spots in rivers that have been used for generations in this country, and it is unacceptable that water quality isn’t monitored there. That is now putting people’s health at risk. So everyone should apply for bathing water status for the rivers they use, because that is exactly what the system is in place for.”

Howard Boyd said: “Water quality absolutely needs to improve, but we also need to recognise that it is a complex combination of action that will allow water quality to improve. I am very clear that it is something that we need to continue to apply urgency and effort to.”

She said that while discharges from combined sewerage outflows were permitted under licences from the agency, a move towards turning rivers – or parts of them – into bathing water areas would mark a significant shift of what was expected in terms of river water quality. But it would require more funding from government.

“We need to make sure there is adequate funding and resources in order to reach the standards,” said Howard Boyd. “We need to make sure that the funding does come through if this happens. Those are the discussions that we will need to have with Defra.”

She defended her agency’s record in monitoring water companies, saying it had been working closely with the watchdog Ofwat to draw up the wholesale price controls for water companies from 2020-25, the PR19, to ensure that water quality in rivers and investment in infrastructure were a key part of spending for the five-year period. The £51bn PR19 includes spending of £4.8bn on reducing pollution, leakage and water use.

“We are very keen to make sure that that money is invested in delivering water improvement – £5bn is a significant amount to be spent on that,” she said.

Howard Boyd pointed to fines, including £20m against Thames Water in 2017, as evidence that the agency was taking a tough approach to incidents of unlicensed pollution.

Ash Smith, the founder of Wasp, welcomed Boyd’s comments. On his group’s plan to apply for bathing water status on the Windrush, he said: “It is the only way that we can see to get the Environment Agency, the water industry and the government to start treating our waterways with respect … We are going backwards in terms of water quality. People have taken their eye off the ball and the water industry has exploited that.”