Bathing water at Instow has failed to reach the standard required by the European Bathing Water Directive. But Combe Martin and Ilfracombe Wildersmouth, which both failed last year, have passed.
The Environment Agency said following a summer of unprecedented rainfall in the South West, the second wettest summer on record, 16 bathing waters in the region had failed their water quality results under the current European Bathing Water Directive, compared to two last year. But, despite the unusually high levels of rainfall, 92% of the 193 beaches in the South West still passed the European standards.
The EA said exceptionally heavy rainfall results in more pollution being washed into bathing waters and warned that due to climate change, these extreme weather events could occur more often.
Richard Cresswell, Environment Agency Director for the South West, said: "Bathing water quality has improved significantly over the past two decades, but this year's significant rainfall over the summer has impacted on bathing water quality around the coast, particularly in the South West.
"During intense rainfall, pollution from farmland, roads, and drains is washed into water courses that finally end up in the sea. Water companies also operate Combined Sewage Overflows to prevent sewage from backing up and flooding people's homes.
"This very wet year has re-emphasised that more needs to be done by water companies, businesses, farmers and local authorities to improve the water at Britain's beaches and meet more stringent water quality targets, which will come into force in 2015. With even tighter standards for our bathing waters coming into force we really do need everyone to take action now."
The Devon sites which failed to reach the bathing water standards are: Instow, Budleigh Salterton, Exmouth, Bantham, Mothecombe, Plymouth Hoe East, Plymouth Hoe West, Shaldon.
Other South West sites to fail are: Somerset: Uphill Slipway beach near Weston-super-Mare; Dorset: Kimmeridge Bay, Lyme Regis Church, Charmouth West; Cornwall, Seaton, East Looe, Bude Summerleaze, Mounts Bay, Wherry Town.