Nuclear power station operators unlawfully allowed radioactive waste to seep from a decontamination unit for 14 years, Chelmsford Crown Court has heard.

Waste leaked into the ground from a sump at Bradwell power station in Essex between 1990 and 2004, the Environment Agency claimed.

Magnox Electric Ltd, which had operated the station, denies 11 breaches of legislation governing the disposal of radioactive waste. Mark Harris, on behalf of the Environment Agency, told the jury that leaks were caused by a combination of poor design and a lack of checks and maintenance. He said the power station was no longer running.

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"The case concerns the disposal of liquid radioactive waste which leaked to the ground from a sump at the site of what is now the former Bradwell nuclear power station," said Mr Harris.

"These leaks occurred on a number of occasions between as long ago as 1990 until discovery of these leaks in February 2004. The leaks were caused by a combination of poor original design of the sump... and, in the period when this company was running it... there was no routine inspection or maintenance of the sump until after the leak was discovered."

The hearing continues.