Fat washed up on Brighton and Hove beaches was flushed out of sewers by heavy rain, according to the Environment Agency.

The Government watchdog says the deposits were most likely fat washed out of sewer pipes, although it is still waiting for the results of laboratory tests.

The agency insisted the deposits posed no threat to health and did not mean lower water quality along Brighton and Hove's beaches.

The public was warned to stay away from the 15-mile stretch of beach between Portslade and Saltdean last weekend, as the tide came in and with it the fat.

Many beaches were still covered in the deposits a week after windsurfers at Hove Lagoon first raised the alarm.

Peter Midgley, the agency's Sussex area manager, said it was not uncommon for fat to be flushed out of sewers and washed on to beaches after heavy rain.

He said the fat was rolled into small balls as it was washed along the pipes and passed through old-fashioned sewage treatment works, such as Portobello.

Mr Midgley said: "It does not mean the water quality is bad. While they can look a bit unsightly for a day or two, it is not a particularly bad environmental problem."

Richard Gregory, of the pressure group Surfers Against Sewage, criticised the agency for claiming the fat deposits did not affect water quality.

He said: "How can they just say it does not affect water quality when it is in the water?"

Southern Water, which operates the sewerage network, said the deposits were not raw sewage.

It believes the fat came from a wreck offshore, which had been disturbed by storms.

People using beaches such as Ovingdean, still have to deal with globules of fat the size of tennis balls.

Beach hut owner Amanda Connelly said: "I am concerned about this mysterious lard. It would be nice to know when is it going to be cleaned-up?"