Nigg Bay in Aberdeenshire is Scotland's most polluted beach by a significant margin, according to a new report.

The Marine Conservation Society also found high levels of pollution at East Bay in Helensburgh, Footabrough in Shetland, and Edinburgh's Cramond Beach.

But Nigg Bay was found to have more than twice the number of pollutants per metre of beach than Helensburgh.

The research forms part of the society's annual Beachwatch survey, which is designed to highlight the dangers to wildlife and aesthetic offensiveness of litter on the UK's shoreline.

Almost 2,000 volunteers recorded and removed 222,704 pieces of debris from 194 beaches around the UK on 15 and 16 September last year.

In Scotland the volunteers found:

• A total of 33,369 items of litter were found over 27.7km on 29 beaches

• An average of 1,207 items/km were recorded, less than Beachwatch 2000 (1,970 items/km) and below the UK average of 1,576 items/km

• Scotland recorded the second highest density of sewage-related debris in the UK (171.6 items/km) after the north west of England (203.9 items/km)

Overall, the amount of litter collected was down on the previous year, but the campaigners said the amount recovered remained unacceptable.

Karen Riley, MCS Beachwatch co-ordinator, said: "Litter harms wildlife by entanglement in and ingestion of debris, decreases tourism revenue, causes loss of fish catches and imposes a massive clean-up cost on affected areas.

"Although the situation is improving, there is still a long way to go to ensure our beaches are clean and safe places for people and wildlife to be."

Ms Riley said the majority of litter could be traced to tourists and visitors to the beach.

Across the UK, the debris found on beaches broke down as:

• 37.2% was litter dropped by tourists and visitors

• 12.2% was fishing debris

• 6.7% was sewage-related debris

• 3% related to shipping.

Together, these four major sources comprised more than 59% of all litter found.

Analysis of all the items found revealed that pieces of plastic were the most commonly dropped item with bits of rope next.

The beach at Balmedie Country Park, on the edge of Aberdeen, was found to be Scotland's cleanest beach.

It was closely followed by Coldingham Bay in the Borders and Berriedale in Caithness.