SOUTH West Water is in the process of investigating 'high frequency' spills from a sewage plant that discharges into the River Avon, or River Aune.
Sewage discharges from storm overflows at the Diptford and Moreleigh plants rose from 128 in 2021 to 207 in 2022, according to Environment Agency data.
That equates in hours of discharge from 450 in 2021 to 1,056 in 2022.
South West Water has responded that work at both sites should reduce the level of spills by the end of July.
The River Avon is a popular spot for wild swimmers. Starting in southern Dartmoor, the river flows through South Brent, near Ashburton, and flows into the sea at Bigbury-on-Sea.
Every year, hundreds of swimmers gather at the river to take part in the Bantham Swoosh, from Aveton Gifford to the sea.
Discharges from storm overflows are supposed to operate in times of heavy rain to prevent homes and businesses flooding. However, critics argue that the sudden rise in pollution does not correlate to increased rainfall.
The discharges into the River Avon at Diptford sewage treatment works rose from 83 in 2021 to 119 in 2022, according to the EA statistics.
Discharges from storm overflows at Moreleigh on Torr Brook, one of the main tributaries of the Avon, rose from 45 in 2021 to 88 in 2022.
SWW said it was committed to achieving an average of 20 spills per storm overflow per year by 2025.
In April, the company was fined a record £2.1m after admitting it caused pollution at five sewage treatment works and pumping stations in Devon and Cornwall.
A SWW spokesperson said: 'We are reducing the use of storm overflows and our plan is working but there is more to do.
'We want everyone to feel confident about water quality and to know that we are serious about reducing the use of storm overflows.
'We've installed 100% monitoring on our storm overflows, ahead of target.