Just when you thought it was safe to forget the rain and make a break for the beach amid a possible, fleeting breakthrough in the weather this weekend, a report on sea-side pollution released today might make you think again. Confirmation that this year's August Bank Holiday marks the climax of a shower-soaked, dreary summer comes in a report by the Marine Conservation Society (MCS) showing a distinct increase in pollution on Britain's beaches.

According to the report, one in eight UK beaches - 71 in total - has suffered a "serious short-term pollution incident" in the first half of the summer, while 16 of the 553 beaches tested failed minimum bathing water quality standards. The tests are based on EC mandatory standards for bacteria. Last year only two of the 520 beaches surveyed failed.

"Heavy rain will periodically sweep waterborne pollutants such as raw sewage, organic refuse and farm waste from the land into rivers and the sea. The problem for swimmers is knowing when that has happened," said the MCS's coastal pollution officer, Thomas Bell, who called for a "Marine Act" to address the problems. "Specific counter-pollution measures are needed including expansion of the sewer system to handle large volumes of storm water, and the rapid improvement of an estimated 2,000 failing combined sewer overflows.

"Increased storm pollution is just one of the many growing pressures on our seas, and MCS is calling for a Marine Act to provide better protection and management for our seas and coasts."

Today's report shows a drop to 86 per cent of beaches that were deemed to maintain a good standard, compared with 94 per cent last year.

Serious damage allowed to affect Britain's beaches could damage Britain's economy, experts have warned. In May, the MCS warned that the flash flooding and extreme weather were contributing to beach pollution. It showed that about 463 of the UK's 1,100 beaches have sewage overflow pipes sited on or near them, which have sent millions of gallons of sewage into the sea and along Britain's beaches.

"We are calling on the Government to provide public information on all bathing beaches, advising swimmers that coastal waters can be temporarily affected by increased pollution, with a consequent risk to bathers' health, after heavy rain," Mr Bell added.

"The sewer overflows that often come out beside beaches have been discharging a lot more. This flood water will also contain other chemicals like fertilisers from fields and this can aggravate problems such as algae blooms off the coast, although we are yet to see that."

Last year, 21 million visitors spent about £14bn at Britain's seaside resorts, of which a record number were commended for having "excellent" beaches by the MCS.

The society also granted 85 of them a Blue Flag award, for which a beach must meet 29 strict criteria regarding litter levels and water quality.