People were told to stay away from 15 miles of Sussex coastline after fat deposits were washed up on the beaches.

Brighton and Hove Council seafront officers advised people to stay away from the shore between Saltdean and Portslade yesterday as Southern Water staff began a huge clean-up operation.

Windsurfers at Hove Lagoon first noticed the problem on Saturday when their wetsuits and boards became covered in the sticky globules.

Sam Edden, duty manager of Hove Lagoon Watersports Centre, called everyone in from the sea.

He said: "I have never seen anything like it before. There was sticky yellow stuff on all the pebbles. There was not a carpet of it by any means but you couldn't help walking on it.

"People did go out in the sea this morning but this stuff is taking a lot of washing to dissolve off their boards and wetsuits and we didn't think it was a good idea for people to go out."

Richard Gregory, of Surfers Against Sewage in Brighton, collected a sample of the substance and wants environmentalists to analyse it for sewage.

He said: "Cooking fat and lard is known to build up in sewers and it is not removed from the water during treatment.

"It would not surprise me if the heavy rains over the last couple of days meant it was all washed into the sea.

"If this has come from the sewers it will also contain sewage. The public should be told exactly what this yellow stuff is made up of as kids are playing on the beaches.

"Someone needs to take responsibility, not only for the short-term cleaning up operation but also for looking for ways to make sure it never happens again."

However, Brighton and Hove Council seafront officer Viki Miller said the fat was not thought to be dangerous.

She said: "It is not pollution and is not by any means sewage. People shouldn't panic - it's not dangerous, just a bit messy."

Ms Miller blamed recent rough seas and high rainfall for the sticky problem.

She said: "It could be anything that has been washed on to the beach from large container ships over the last couple of days.

"It has happened once before and is probably a result of the rough weather. We have had a lot of seaweed washed up on the beaches as well."

Southern Water workers were cleaning the beaches yesterday and it was hoped the problem would disappear after this morning's high tide.

Warning notices have been put up on Brighton and Hove beaches alerting people to fat deposits on the shingle.

A council spokeswoman said: "Fortunately it is not the height of the swimming season."

She said the coastline between Bexhill and the Solent had been contaminated.