SCOTLAND has fewer beaches hitting a top rating, with heavy rainfall blamed for the fall in water quality.

The disappointing results for Scotland in the latest Marine Conservation Society's (MCS) Good Beach Guide comes as a record number of UK beaches achieved its "recommended" status.

The figures, based on testing carried out last summer, show 516 out of 754 UK beaches were recommended for "excellent" water quality. That is an 8% rise on the previous year's figures and is the best set of results in 25 years of the guide.

Forty-five Scottish beaches were in the top category, from Coldingham Bay in the south- east Borders to West Voe in Shetland, Achmelvich in Sutherland and Culzean in South Ayrshire.

But this represented only 41% of the country's beaches, a 5% drop on the previous year after the country was hit by heavy summer downpours and above- average rainfall in 2011.

Four designated bathing beaches in Scotland failed basic European standards. They were Eyemouth in the south-east Borders, Lossiemouth East in Moray, Irvine East in North Ayrshire and Sandyhills in Dumfries and Galloway.

Three beaches not designated as bathing areas – which do not get as many samples of water taken – also failed. They were Cramond in Edinburgh, Lower Largo in Fife, and Largs main beach in North Ayrshire.

Rachel Wyatt, MCS coastal pollution officer, said: "It is important local authorities, water companies and environmental regulators don't become complacent about continued environmental improvements.

"If that happens we could see a drop in the number of beaches recommended by us in the future."

She said one of the threats to bathing water quality was overflow pipes which discharge raw sewage into rivers and the sea from sewer networks when heavy rain overloads the system with water from street drains.

The MCS has said there are about 31,000 of these combined sewer overflows around the country, more than three-quarters of which are not monitored. It is concerned some of them are discharging untreated sewage dozens or even hundreds of times a year, far in excess of guideline levels.

MCS pollution programme manager Robert Keirle said: "Combined overflows are an essential part of a well-maintained sewerage network. If you didn't have them in times of flood, sewage would back up in our toilets and manhole covers in the street. But we are worried about them being used too frequently by water companies, not just for emergencies."

He called for monitoring of all overflow pipes to find out how often they were discharging polluted water.

The other risk to bathing waters caused by heavy rain is diffuse pollution washed into rivers and coastal areas from the countryside and towns as a result of downpours.

Mr Keirle said pollution could be reduced if dog mess was cleaned from the streets before it was washed into the river system and animals were fenced away from water courses in the countryside.