The water quality of Britain’s beaches is being jeopardised by thousands of unregulated overflow pipes that dump raw sewage into coastal waters and rivers, an investigation has revealed.

The Sunday Times has obtained details of 3,500 overflow pipes operated by water companies that allow them to dump unlimited amounts of raw sewage in more than 80 rivers and along sections of the coast.

“There is no limit on the amount of sewage that can come out of these overflows,” said Thomas Bell, coastal pollution officer of the Marine Conservation Society (MCS), which has obtained details of the locations of the sewer pipes under freedom of information laws. “They represent a licence to pollute.”

Among the overflows are:

— More than 60 operated by South West Water, including pipes on the River Torridge, which flows to a popular Devon beach.

— More than 250 outlets operated by Yorkshire Water, including sewage flowing into the North Sea.

— Sewage overflows on the River Don, where thousands of fish were killed by sewage pollution in 2006.

— An overflow operated by United Utilities near Manchester, which was blamed for polluting a fishery in 2005.

The 3,500 sewage overflows were among more than 20,000 identified when the water industry was privatised. Most had environmental conditions imposed on them but these are still outstanding.

There are also about 500 regulated sewer overflows on Britain’s beaches that are supposed to operate only after heavy rain. Swimmers and surfers complain that these are operating more regularly to relieve pressure on sewage systems said to be “at bursting point”.

Despite a £10 billion investment programme by water companies since privatisation, about one in four beaches still fails to qualify for the European Union’s top category.

The investment has ensured that 96% now meet the lower mandatory standard, but this still means that a swimmer has a 14% chance of contracting a bacterial or viral infection.

The MCS last week called for tighter controls and improved monitoring of sewer overflows. It said the Environment Agency had failed in its duty by not imposing strict environment conditions on the 3,500 sewage overflow pipes.

The agency said that it had concentrated its resources on dealing with sewage overflows that had been the subject of complaints or had known problems.

New restrictions were now being planned on the 3,500 overflows, it said.

The water industry says it is replacing many of the sewage overflows that cause problems and added that they are used only when necessary to expel sewage and flood water.

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