Half of all the UK beaches which failed to meet the minimum European Commission (EC) standards for water quality this year are in the South West, a report today shows.

But the campaign group Surfers Against Sewage (SAS) claim many more Westcountry beaches with EC credentials remain a serious health hazard, with one in seven bathers likely to become ill after a dip.

Overall, beaches and bathing spots in England and Wales saw record numbers achieve the higher guideline standards, Environment Agency (EA) figures have revealed. Some 86 per cent satisfied the standards for 2010 – up six per cent – with 98 per cent achieving the mandatory minimum EC standard.

However, Andy Cummins, SAS campaign director, said it was important to note that the results were based on standards set in 1976 and described the continuing failures as "woefully inadequate".

He said: "The guideline standard represents a one-in-20 chance of catching gastroenteritis and that is just from splashing around for five minutes. If you go under the water that can rise dramatically to as much as one in seven. These standards are not anything to shout about and are not a standard to protect public health.

"We are warning the water industry that pride comes before a fall. When tougher regulations come in in 2015 we are predicting mass failures and a lot more areas of concern."

Ten out of 493 beaches and bathing spots monitored failed to meet minimum standards, compared to seven last year. This number included Mothecombe, Seaton and Instow in Devon, Lyme Regis in Dorset and Seaton in Cornwall.

Environment Agency (EA) chief executive Paul Leinster praised an improvement which has seen the number of beaches attaining the highest quality status "almost triple over 20 years".

He said: "The EA is working hard with others to drive improvements and tackle all sources of pollution alongside beach users, local authorities, farmers, land managers and water companies."

But SAS claims not enough is being done. The group blames many of this year's failures on combined sewer overflows (CSOs), which discharge screened, but untreated, sewage into rivers.

This summer SAS forced Keep Britain Tidy to lower its prestigious Blue Flag at beaches which fail to issue real-time warnings when CSOs pollute waters.

It launched a rival Brown Flag scheme to highlight discharges and exposed failings at Polzeath, Gyllyngvase and Carbis Bay in Cornwall and Challaborough and Bigbury-on-sea in Devon.

A trial scheme now warns beach users at Gwithian and Porthtowan of discharges.