Figures released by The Rivers Trust reveal there were 1,117 releases of raw sewage in thearea for a total of 12,613 hours, a quarter of all spillage hours in Gloucestershire.
Councillor for Bourton and Northleach, Paul Hodgkinson, said the figures are “simply staggering”.
He added: “This is a practice that is meant to be used only in exceptional circumstances, yet it is blatant, even to the most casual observer, that it has become a routine practice.
“Healthy rivers are vital for biodiversity and human health but, last year Gloucestershire’s rivers saw 137 hours of sewage dumping each and every day that is destroying this fragile ecosystem.”
Across Gloucestershire, there were 5,178 Combined Sewage Overflows (CSO), for a total of 50,602 hours.
CSO’s are intended to be used during storms to prevent flooding in homes and businesses.
Severn Trent made up almost three-quarters of release hours in the area, with 37,602.
A spokesperson of the water company said: “We’re passionate about making a positive impact on the communities and the environment where we live and work.
“Our region’s rivers are currently the healthiest they have been since the Industrial Revolution.
“We’re working hard to use overflows less and investing £100m a year to go even further in improving rivers so that nature can continue to thrive.”
Thames Water meanwhile was responsible for 17 per cent of releases in the area.
A spokesperson said: “Our aim will always be to try and do the right thing for our rivers and for the communities who love and value them.
“We regard all discharges of untreated sewage as unacceptable and will work with the government, Ofwat and the Environment Agency to accelerate work to stop them being necessary and are determined to be transparent.
“We have a long way to go – and we certainly can’t do it on our own – but the ambition is clear.”
Thames Water has committed to a 50 percent reduction in the total annual duration of spills across London and the Thames Valley by 2030.
The company also has planned investment at several sites, including Moreton, and will be carrying out work on manholes and pipes in Bourton to prevent excess water from entering its sewer network.
Another company in the area is Wessex Water, responsible for 3.8% of the release hours.
A spokesperson said: “We’re committed to completely eliminating the discharge of untreated sewage, starting with storm overflows that discharge most frequently and those that have any environmental impact.
“Every month we’re investing more than £3 million to reduce storm overflows across our region, with £150 million being spent between 2020 and 2025.”
Councillor Paul Hodgkinson added that the county MPs need to be doing more to tackle the issue.
He said: “Despite this clear evidence, Conservative MPs are letting water companies get away with it.
“Five of Gloucestershire’s MPs failed to support an amendment to the Environment Bill, which would have put a legal duty on these companies to phase out sewage dumping.
“It’s time to send a message once and for all that this filthy practice has to end.”
Cotswold MP Sir Geoffrey Clifton-Brown has been contacted but at the time of writing, has not provided a response.