Many hotel swimming pools in some of the most popular holiday resorts for British tourists are a health risk, a Consumers' Association survey published today in Holiday Which? magazine has found.

One in four pools tested for bacteria in Majorca and Corfu were condemned as a health hazard. The CA took samples from 80 pools to test for microbiological contamination. Twenty posed a considerable risk to bathers.

Six of them were heavily contaminated with faecal bacteria. Others had sufficiently high levels of bacteria to represent a hazard.

Another 29 pools were a potential health hazard, while just two of the 80 were given a completely clean bill of health.

Majorcan resorts where pools were tested included Alcudia and Puerto de Pollensa, while most of the Corfu pools were in the resort of Sidari.

The concentration of chlorine in seven pools was high enough to bleach bathing suits and was likely to cause irritation to eyes and skin.

Five pools contained no traces of disinfectant, putting swimmers at risk of infection, particularly ear infections. Holiday Which? managing editor Kim Winter said: "Our evidence of gross bacterial contamination shows the apparent incompetence of most hotels at maintaining effective levels of disinfectant in their pools, posing a serious health hazard."

The CA advises people not to swim in pools which are overcrowded, since water treatment systems may be overwhelmed, or if chlorine smells pungent, an indication that it had reacted with pollutants.