More than one in three British beaches pose a health risk to swimmers, according to startling figures released by the department for environment, food and rural affairs (Defra) last week - the worst results since 2001.

Analysis of bathing water at Britain’s 587 officially designated bathing beaches revealed that 207, or 35%, failed to meet World Health Organization guideline safety standards for swimmers’ health. Of these, 24 - including popular holiday spots such as Rock, in Cornwall, Combe Martin, in Devon, and Sandgate, in Kent - failed even to pass the much less stringent UK minimum standards for faecal and bacterial contamination.

Defra blames “exceptionally wet weather in July, August and September” for what it describes as the “slightly lower standard of the water this year”. It points out that 10 of the 15 English beaches that failed were in the southwest, which was hit particularly hard by heavy rainfall last summer.

“Also, the coast is ringed by a network of combined sewer overflows which discharge storm water and raw sewage into the sea whenever the sewers flood,” explained MCS pollution officer Thomas Bell. “We believe this network needs significant new investment to reduce its pollution impact, as well as new measures to tackle storm runoff from farmland and city streets.”

Clean water campaigners Surfers Against Sewage (SAS) accused the government of failing to address environmental challenges caused by climate change, predicting that even more British beaches will be contaminated by pollution if summers continue to bring intense rainfall, as expected, in the coming years.

“The last two summers have been exceptionally wet, and water quality has suffered as a result,” said SAS campaign manager Andy Cummins. The Marine Conservation Society “We need to be fully prepared for future (MCS), a charity dedicated to the summers to be disrupted by extreme protection of the British coast, said the weather events.” report reflected a “worrying trend towards worsening pollution on Britain’s beaches”, adding that long periods of heavy rain had washed pollutants such as agricultural fertiliser, street debris and animal waste into the sea.

Times recommends

• Oasis of the Seas: the Times review
• The 20 best new year party places to stay
• Green Spaces 2009: are you the winning writer?