Raw sewage was 'dumped' into the river Tone hundreds of times last year.
Untreated sewage flowed into the river, which runs through Wellington, on 337 occasions in 2022, data from Top of the Poops has shown.
The Tone is one of many waterways across Wellington and West Somerset into which raw sewage has been discharged.
Sewage overflows ran into the Doniford stream 109 times, and into the River Avill 106 times last year.
Wessex Water is the firm responsible for most of the water and sewerage operations across Somerset. West Somerset MP Ian Liddell-Grainger has said the company had "an appalling record for dumping raw sewage into Somerset’s rivers."
Mr Liddell-Grainger has waded into the sewage row on multiple occasions. In his most recent intervention he accused the company of sabotage, saying:
"Water companies which have preferred to reward shareholders rather than invest in upgraded treatment systems are in the process of sabotaging the British seaside’s newly-acquired reputation as a clean and safe place to holiday.”
The water company denies that they 'dump' sewage into watercourses, saying that storm overflows are a legal mechanism to prevent the flooding of properties.
A spokesperson for the company said: “Rivers and streams in West Somerset are not designated bathing sites but we absolutely agree that storm overflows aren’t fit for the 21st century and our long-term aim is eliminating the need for them.”
Data from The Rivers Trust, shows that the Mitchell's Pool Pumping station in Wellington, which is operated by Wessex Water, overflowed into Haywards Water 20 times last year.
Also run by Wessex Water, the Hillsmoor Water Recycling Centre near Wiveliscombe, discharged overflow into a tributary of Hillfarrance Brook 27 times last year.
A spokesperson for Wiveliscombe Extinction Rebellion said: "The rivers and streams around Wiveliscombe and Wellington feed into the river Tone. The Rivers Trust report that all rivers in Britain are now polluted and this means ours too.
"Privatised water companies are beholden to their shareholders and the health of local people and wildlife comes a poor second. The government’s plan is slow, limited and underfunded. Water testing is left to local volunteers as the Environment Agency don’t have the staff.
"We are calling for the water quality of Somerset’s rivers to be taken seriously and made a top priority and we at WiveyXR will continue to campaign and draw attention to this issue."
In February, Wellington's MP Rebecca Pow, and a junior environment minister, said the government were working to tackle the issue of sewage overflows.
She said: "Much misinformation has been spread regarding sewage in water and yet this Government is doing more than any government to clean up our waters and no one voted for sewage to go into rivers, despite spurious claims, quite the contrary.
"Firstly, the original Victorian storm sewage overflows, designed for emergency use during extremes of rain to prevent sewage backing up in our toilets have been used far too frequently by water companies despite permits to limit their use.
"Through the Government’s Storm Overflows Discharge Reduction Plan launched last August 2022 water companies are required to deliver the largest infrastructure programme in water company history - £56 billion capital investment over 25 years."
Throughout all of 2022, Wessex Water oversaw 21,878 sewage overflows, lasting for 129,957 hours, across 994 locations in their service area.