The government must clamp down as a matter of urgency on water companies which continue to pollute bathing waters, Somerset MP Ian Liddell-Grainger has warned.

He says unless firm action is taken, much of the progress made in cleaning up Britain’s beaches could be reversed.

During its EU membership and in order to comply with a succession of water quality directives, the UK invested hundreds of millions in sewage treatment plants to end the discharges of untreated effluent to the sea.

Dozens of beaches were able to fly the European blue flag – denoting the highest standards of cleanliness and safety.

But figures just released show water companies discharged raw sewage into coastal bathing waters used by families and holidaymakers 25,000 times in the past year.

Untreated effluent poured into the sea for a total of 160,000 hours through storm overflows, ending up on beaches as far apart as Clevedon and Scarborough.

The Environment Agency posts official warnings on those days when bathing water quality is compromised but, said Mr Liddell-Grainger, not all beach users would necessarily read them.

“And simply saying the water isn’t fit to swim in on a particular day is just not good enough,” he said. “It’s merely tackling the symptoms rather than the cause.

“We have made great strides in the last 40 years in cleaning up beaches which were once grossly polluted by sewage. Resorts around the coast have rightly been able to attract holidaymakers by assuring them of the high quality of local bathing waters.

“But water companies which have preferred to reward shareholders rather than invest in upgraded treatment systems are in the process of sabotaging the British seaside’s newly-acquired reputation as a clean and safe place to holiday.

“The water industry has been making all sorts of noises about bringing in improvements but it needs to have its feet held to the fire in order that these are introduced with no undue delay. And in the meantime I would suggest that heavy, on-the-spot penalties for any further breaches would be an excellent way of concentrating minds.”