Almost every beach in England and Wales meets Europe's highest cleanliness standards, the Environment Agency says.
Tests reveal the quality of water in 97% of bathing sites is sufficiently good to be classified "excellent".
But the agency says the results were based on early season sampling and could change over the coming months.
It says the recent spell of good weather and action to reduce pollution from farms and sewer overflows are responsible for the improved results.
Last week the Marine Conservation Society rated 421 of 769 UK beaches as excellent - 33 more than 2009, but below the 505 rated highly in 2006.
Its annual Good Beach Guide revealed more beaches have excellent water quality than last year, but pollution has worsened since 2006.
The Environment Agency tests show a rise in the number it classifies as excellent of almost a fifth, from 76% 10 years ago to the current 97%.
Inspectors take weekly water samples at 494 sites to measure pollution levels between May and September each year.
A total of 14 beaches were rated "good" while one - Staithes in North Yorkshire - was given a "poor" rating due to levels of bacteria from sewage and livestock waste.