BNFL said it is implementing a range of improvements

The Environment Agency served the enforcement notice on Thursday.

It follows an incident earlier this year when two pieces of rubber gasket, contaminated with radioactivity, were found by BNFL on beaches in Cumbria.

BNFL said an inquiry had been carried out and improvements were being made to prevent a similar incident occurring.

Although the risks to the public on this occasion were low, this type of incident is both undesirable and preventable Andy Mayall, Environment Agency

Both gaskets were discovered separately during routine checks of the Sellafield and Seascale beaches in January and February.

Tests revealed the radiation levels of both items were found to be low, presenting little potential hazard to the public, but they were above the agreed reporting levels.

The Environment Agency said in a statement: "The notice has been issued because of BNFL's failure to comply with a condition of their authorisation granted to them by the Environment Agency to dispose of low level radioactive waste at their Sellafield site in Cumbria."

Andy Mayall, the Agency's Nuclear Regulator, said: "Although the risks to the public on this occasion were low, this type of incident is both undesirable and preventable. That is why we have issued the enforcement notice."

A BNFL spokesman said: "The discovery of gasket material on the beach was publicly reported by us at the time of the event.

"Since then, we have carried out a detailed internal inquiry and are already implementing a range of improvements, including all of the work required by the Environment Agency We are determined to learn from this event to ensure that no repeat occurs."