Environmental campaigners claim the UK has failed to cut down on radioactive discharges from Sellafield over the past five years.
Sellafield nuclear reprocessing plant
Ministers from across Europe are gathering in Bremen, Germany, for
the Ospar Convention to discuss the protection of the marine environment of the north-east Atlantic.
It is the first such gathering since 1998 when Deputy Prime Minister John Prescott pledged the UK had shed its "dirty man of Europe" image and would reduce radioactive discharges from Sellafield into the sea.
Greenpeace claims that since then the UK has failed to live up to its promises, and has called for the closure of Magnox reprocessing plants at Sellafield.
It claims discharges from British Nuclear Fuel's (BNFL) Sellafield facility have increased and are set to double over the next few years.
But BNFL says Greenpeace is trying to mislead the public over the level of discharges from the plant.
Anti-nuclear campaigner Jean McSorley said: "The British Government has misled the public and the Ospar countries with its hollow promises to cut nuclear pollution when in fact Sellafield is to discharge even more radioactive waste into the North Atlantic.
"The only way to tackle Sellafield's discharges into our seas is to shut down BNFL's dangerous, old and loss-making Magnox reactors.
"Reprocessing nuclear fuel from these plants causes most of Sellafield's shameful pollution record."
But a BNFL spokesman said: "They are clearly trying to mislead both the British public and member countries of the Ospar convention, at a time to coincide with the meeting in Germany.
"Discharges from Sellafield are now less than 1% of what they were in the late 1970s and early 1980s.
"We are currently witnessing a small rise in discharges, and we have always said this would be the case with these discharges brought about by decommissioning plant.
"It is no secret that Magnox is being phased out by 2012, which Greenpeace well knows."
Environment minister Elliot Morley will join ministers from 14 countries to discuss marine pollution.
It is the fist time ministers have met under Ospar since the meeting in Sintra, Portugal, five years ago which set commitments for action on radioactive discharges.
The Royal Society for the Protection of Birds said ministers at the Ospar conference are on the verge of taking key steps towards halting the decline of marine life in Europe's seas.