Ten beaches and bathing spots in England and Wales, including Blackpool beaches and waters on the Lancashire coast, failed to meet strict new EU standards for water quality this year, figures have shown.
The statistics from the Environment Department and the Welsh Government also showed that a record 89% of the bathing waters, a total of 447 sites, met the tough European standards due to come into force by 2015, up from 86% which met the "guideline" grade last year.
The percentage of those meeting basic levels of water quality is much the same as in 2010.
There were nine sites which failed in England and one in Wales, at Llandudno west shore.
Blackpool central and south beaches, St Anne's North, St Anne's Pier, Heysham Half Moon Bay and Fleetwood, all on the Lancashire coast, failed the basic water quality tests.
So did Walpole Bay, Margate, and Ilfracombe Capstone and Combe Martin on the north Devon coast.
The Environment Agency said beaches had improved drastically over the past 20 years, when only three-quarters of beaches and inland bathing waters managed to meet the basic grade.
Christine Tuckett, head of bathing waters at the agency, said: "Over £8 billion has been invested by water companies and the Environment Agency to upgrade our sewerage systems and reduce pollution.
"As a result, almost all of our beaches meet the minimum standards now, compared to just three quarters in 1991.
"But new, stricter standards will come into force in 2015, and we are working with water companies, farmers, local authorities and beach managers to tackle persistent sources of pollution and make sure that as many beaches as possible pass these standards."
The Environment Agency said it had secured a further £4 billion in investment in environmental improvements by the water industry between 2010 and 2015, including for bathing spots, with 90 projects improving water quality at 37 coastal sites.