WWF-UK have warned targets to clean up England's rivers are "very unlikely" to be met if the country's waterways continue to be used as "dumping grounds for sewage".
The charity's claims come as the Environment Agency said, "water quality is now better than at any time since the Industrial Revolution," despite only 14% of rivers in England and the Scottish and Welsh borders being close to their natural state.
The regulator predicts that 75% of rivers could be brought to ‘good’ status by 2027, the latest allowable deadline in the EU Water Framework Directive (WFD).
But the charity said the Environment Agency's target reminds elusive if the government do not take necessary action.
Dave Tickner, Chief Adviser, Freshwater at WWF said: “It is very unlikely that the Environmental Agency’s target of 75% can be achieved unless the government takes the actions we are advising.
“We know that fewer than 20% of our rivers are in a good state and that simply has to change. We must stop using our precious waterways as dumping grounds for sewage and farm pollution. And we need to be more efficient in our use of water so that rivers aren’t sucked dry.”
Mr Tickner said with Brexit looming, the government must "fast-track flagship legislation" to protect and restore waterways as well as investing in policing rivers to prevent water companies and the agricultural industry from using them "as open sewers".
Dr Andrew Singer, senior scientist at the Centre for Ecology and Hydrology told ITV News it was "likely" that no river in the UK was low enough in pathogens - that is bacteria or virvus that cause disease - to be safe to swim in.
"No UK river is designated as a bathing water," he said.
"If it was WWTP (Wastewater Treatment Plants) would be regulated as such which would mean they would need to actively remove pathogens in the effluent going into the river.
"No such treatment is present and as such all rivers likely exceed limits on pathogens above bathing water tolerance. It would cost the water industry a lot of investment to get to the point where they could reliably comply."
The Environment Agency said 97.9% of rivers in England met the minimum required ‘sufficient’ standard in 2018 and 67.1% achieving ‘good’ or ‘excellent’ quality for bathing.
Luke Pollard MP, Labour’s Shadow Fishing, Flooding and Water Minister said "more needs to be done" to ensure rivers were clean enough to swim in.
Responding to the WWF warning, Mr Pollard said: “There is a collective blame of the water companies, the government, as well as those land owners polluting our waterways. More needs to be done to make our rivers cleaned enough for swimming and, perhaps more importantly, pollution free for fish, birds, insects and mammals."
WWF is calling for ambitious measures in the upcoming Environment Bill, including nature recovery networks, which will help halt the declines in wildlife. The charity also wants to see an independent watchdog to hold the government to account on the state of the environment.
According to a 2017 report by WWF, much of the pollution in England's waterways is caused by outdated treatment facilities.
The Environment Agency permits water companies to spill untreated sewage into rivers during extreme rainfall, but they are discharging even when there is light rain due, the charity says, to "insufficient capacity in the system".
The latest figures on Britain's waterways come from Defra's annual Environmental Performance Report (EPA), published in July.
At the time, chair Emma Howard Boyd states that: "there is no getting away from the fact that performance in 2018 was simply unacceptable."
In a statement in response to WWF's claims on Thursday, the agency said: “Water quality is now better than at any time since the Industrial Revolution, largely due to the work of the Environment Agency and the £25 billion of investment that we have required water companies to make.
“To sustain this improvement, we are taking robust enforcement action against those who pollute our waters and in the last four years we have prosecuted water companies 40 times with fines totalling £33 million.
“But we are not complacent. Climate change and population growth are adding to the pressures on water and this is a big challenge for all of us – landowners, regulators, businesses, government and society as a whole.”