By Alex Kirby BBC News Online environment correspondent

Campaigners say the amount of litter found on the UK's beaches in 2001 was slightly down on the two previous years.

But they say even the reduced levels are unacceptable, aesthetically offensive and dangerous to wildlife.

Marine litter is on the agenda of the North Sea Ministerial Conference, which opens in Norway on 20 March.

It is expected to agree an urgent need to reduce the damage litter causes.

The campaigners were taking part in Beachwatch 2001, the ninth nationwide survey of beach litter organised by the Marine Conservation Society (MCS).

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

Perilous encounter

They found the average density of litter was lower than in 1999 and 2000. But MCS said the levels found were unacceptable, and threatened marine creatures as well as spoiling the natural beauty of the coasts.

Karen Riley of MCS said: "The amount of litter collected in Beachwatch 2001 shows an 11.5% decrease on the last year's figures.

Kingfisher nearly came to grief

"Although encouraging news, this level is still higher than that recorded in 1994. There is still a long way to go to ensure our beaches are clean and safe places for people and wildlife to be."

The yachtswoman Ellen MacArthur has written a foreword to the Beachwatch report.

During last year's Vendee Globe race her boat Kingfisher struck an underwater object, possibly a container, which severely damaged its hull.

She said afterwards: "At best the collision put paid to my chances of winning the race, but at worst it could have crippled my boat or even sunk her.

"I was lucky. But it made me all too aware of the amount of litter in our oceans and on our beaches."

The Beachwatch survey found that more than a third (37.2%) of all litter found had been dropped by tourists and coastal visitors. It included crisp and sweet packets and cigarette ends.

Careless habits

Next came fishing debris (12.2%), items from sewage (6.7%), and litter from shipping (3.0%). Litter which could not be traced to any recognisable source accounted for 39.8% of the total.

Karen Riley told BBC News Online: "A lot of our awareness-raising is aimed at tourists, trying to get them to clear up after themselves.

"Most in the shipping and fishing industries do do their best, though some still don't realise the implications of their actions.

Volunteers set out to scour the beaches

"Litter can trap sea creatures - discarded nets, for instance - and it can kill them in other ways.

"Turtles and cetaceans sometimes mistake plastic bags and balloons for jellyfish, and can starve when they swallow them.

"I hope the North Sea conference will help to make it easier to impose the penalties that already exist on people who drop litter that spoils our beaches."

Other items the Beachwatch teams found included a set of false teeth, a pair of underpants, numerous bags of dog mess, and a boomerang - which did not come back.