Minister for the Environment Dick Roche tonight claimed a new enforcement action issued against British Nuclear Group Sellafield Ltd was further evidence of fundamental safety failures at the Cumbria plant.
Mr Roche said he would raise the safety record of the plant across the Irish Sea with British Trade and Industry Minister Alistair Darling in their forthcoming meeting.
The UK Environment Agency instigated the action today following a leak at one of the storage ponds at the site in February 2006.
It occurred during a planned test of instrumentation, which required the water level in the storage pond to be raised temporarily.
However, the water level remained at a higher level than planned, which caused water to leak from a gap in an expansion joint of the pond wall.
A small amount (approximately 8 cubic metres) of radioactive water was lost from the pond but was safely collected in the effluent system designed for such incidents.
Minister Roche said that while this incident involved no escape of radioactivity to the environment and the amount of leaked contaminated water was small, it was another example of the ongoing safety failures at the plant.
"This incident which resulted in the enforcement action by the UK Environment Agency might be considered minor when considered in isolation, however it is the ongoing accumulation of a large number of incidents over a long period of time that point to fundamental failures in safety management and culture at the plant," he said.
"The evidence of a fundamental failure of safety management and culture at the plant continues to mount.
"It requires a significant response from the UK authorities and this is a matter which I shall raise in my forthcoming meeting with the new UK Secretary of State for Trade and Industry, Alistair Darling."