Around 600million litres of sewage-contaminated water enters the River Roding and its tributaries each year, according to a new study.

The research indicates that sewer misconnections and faulty drainage infrastructure are causing 240 Olympic-sized swimming pools worth of sewage to flow directly into the river annually.

Environmental charities Thames21 and the the River Roding Trust monitored more than 70 outfalls and tributaries over a six-month period.

Cran Brook was highlighted as the single most significant source of sewage pollution, which is caused by a mix of faulty infrastructure, “widespread misconnections,” and seepage from a landfill.

Sewer misconnections occur when wastewater from toilets, bathrooms or kitchens is incorrectly connected to a surface water drain, the charities say.

They are now calling on Redbridge Council, Thames Water and the Environment Agency to “urgently accelerate investigations and rectify these chronic sources of pollution”.

However, Thames Water says that while it is working on solving the issue, it may take a year up to a year.

Chris Coode, the CEO of Thames21, said people deserve “clean and healthy rivers” amid an “unacceptable threat to water quality, wildlife and local communities”.

He said: “This is a shocking amount of sewage-contaminated water.

“Six-hundred-million litres is a staggering figure and a disastrous threat to this precious river and its tributaries.

“Particularly concerning is the evidence of pollution entering the River Roding and its tributaries during dry weather. This highlights the urgent need for all river stakeholders to tackle misconnections and to identify and address the other sources of pollution entering the catchment.”

Paul Powlesland, founder of the River Roding Trust, said: “The River Roding is now the first river in England where we know the location of all the illegal sewage outfalls and, crucially, can scientifically rank them in order of harm.

“We now need Thames Water and the Environment Agency to fix the most damaging illegal outfalls as a matter of emergency.”

A spokesperson for Thames Water told the Local Democracy Reporting Service it was undertaking a surface water outfall programme (SWOP) and had so far “identified a large proportion of the area is showing signs of pollution, the majority of which are due to third-party misconnections in private households and buildings”.

They continued: “Due to the size of the catchment, this programme may take up to a year to complete and will be dependent on owners granting us access for the survey or a ‘warrant of entry’ application being made to the court.

“Most misconnections will have been done entirely by accident but the responsibility remains with the property owner, which is why we would urge freeholders or developers fitting new connections to make sure that they’re plumbed in properly.”

Meanwhile the Environment Agency said it was “reviewing the findings of the study to take forward any actions which the Environment Agency can act on,” having met with the River Roding Trust last week.

“We know that misconnections are a major contributor to poor water quality across North London’s rivers,” a spokesperson said..

“We have been working with the River Roding Trust, Thames 21, Redbridge Council and Thames Water projects to identify and rectify these misconnections on the Roding and work has begun on a project for the Cran Brook at Valentines Park.”

Redbridge Council said the levels of pollution were “unacceptable” but the responsibility lay with Thames Water.

Councillor Jo Blackman, cabinet member for the environment, said: “The levels of pollution in the River Roding are both concerning and unacceptable and that’s why we are doing all we can to address the situation.

“We have invested £3 million to improve water quality and have several projects underway. This includes water quality testing and desilting across our lakes, as well as opening up a buried stream and a filtering mechanism to improve water quality of the Cran Brook.

“However, the major source of the pollution problem in the River Roding stems from sewage discharges and sewer misconnections, and it’s something that Thames Water must address by stepping up investment in the local sewer network and their monitoring.”