A water company which allowed sewage to flow into a stream has been fined £10,000.

The incident happened after a pipe owned by Southern Water became blocked, allowing the effluent to enter Bevan Stream at Plumpton Green on March 14 last year, Lewes Magistrates heard yesterday.

It is the 46th time the Worthing-based firm has been convicted of illegally discharging products into waterways since July 1990.

Since then it has been fined £128,000 and received eight formal cautions.

Peter Bilbrough, prosecuting on behalf of the Environment Agency, said a resident living near Strawlands Pumping Station alerted them after seeing sewage entering the stream.

He said: "An inspection of the stream revealed that the pollution could be seen at least 400 metres downstream and the officers observed a few small fish struggling on the surface of the water and several dead invertebrates."

Mr Bilbrough said although the stream was not harmed, small creatures died as a result of the incident, which is thought to have lasted about two hours.

He said: "In this day and age all those responsible for handling polluting or potentially polluting matter are expected to take care to ensure that there is no risk that the environment will suffer."

The pollution happened after a blockage caused sewage to spill out through an overflow, he added.

Fiona Chantrey, representing the water company, said the sewer that caused the accident had since been replaced as part of a £64,000 improvement scheme and the firm was confident there would be no more leakages.

A spokeswoman for the firm said after the hearing: "Although sewage leaked into a tributary of the Bevan Stream, emergency action by the company quickly unblocked the sewer.

"In a comprehensive clean-up operation, a Southern Water drainage crew then flushed the stream with tanker-loads of water, helping to limit any environmental damage.

"Southern Water apologises for what it believes was an isolated incident, but the company is also pleased that the quick response of its staff once the problem came to light helped protect the stream."

In addition to the fine, the company was also ordered to pay £600 costs.