Dozens of beaches, including 15 in the South West, are at risk of failing tough new standards for water quality, the Environment Agency said as it launched its summer monitoring programme.
From next year, more stringent European Union regulations will be brought in for bathing spots around England, and the agency is warning that around 40 beaches are on track to fail if action is not taken to tackle pollution ending up in the sea.
They include Lyme Regis Church Cliff Beach; Burnham Jetty North and Weston-super-Mare Uphill Slipway.
If beaches fail on water quality standards under the new EU rules, local authorities will have to display a sign advising against swimming.
More than 400 beaches will be tested weekly between now and September, with a total of 8,400 samples taken.
The Environment Agency said nine out of ten swimming spots were already meeting the new standards.
But there were still areas where pollution was a problem, caused by agricultural run-off, sewage overflows, animal and bird faeces on beaches and households and businesses with badly connected drains, the agency said.
Water companies, local authorities and the Environment Agency were working to sort out the problem.
Paul Hickey, deputy director of water quality at the Environment Agency, said: "The seaside economy in England is worth around £3.6 billion a year – and every improvement in bathing water quality helps.
"With one year to go until the new EU standards come into effect, the Environment Agency is focusing efforts on the small number of problem sites."
BEACHES ON TRACK TO FAIL
Lyme Regis Church Cliff Beach; Ladram Bay; Budleigh Salterton; Teignmouth Town; Mothecombe; Seaton (Cornwall); East Looe; Gorran Haven Little Perhaver; Porthluney; Porth; Instow; Ilfracombe Wildersmouth; Combe Martin; Burnham Jetty North; Weston-super-Mare Uphill Slipway