If other nations refuse to give Britain the option to start dumping nuclear waste after a 10-year moratorium, then Britain will not sign. That would mean it could not come into force, as it has to be signed by all 12 European coastal nations taking part.
The Government's stance is revealed in leaked briefing papers written by civil servants for the environment minister, David Maclean, before a meeting starting tomorrow which is planned to end with the treaty-signing on Tuesday. The treaty would update two 20-year-old agreements on marine pollution, the Oslo and Paris conventions.
The Government insists that it is not dumping radioactive waste at the moment, but believes that there could come a time when the safest way of disposing of bulky radioactive items such as parts of decommissioned nuclear submarines and power stations is to dump them in deep waters.
Britain is willing to promise never to dump any high-level radioactive waste, the most dangerous kind.
The Government will also accept a moratorium on dumping any kind of nuclear waste for a decade - it does not dump any at present. It promises to carry out research before any decision to begin of disposing radioactive waste at sea, and to consult with other North Sea nations.
But, states the briefing paper, Ireland, Spain, Finland and perhaps Iceland have been unwilling to accept such a compromise. France, the only other nuclear power involved in the treaty, tends to align itself with Britain on the nuclear question.
'We must retain the right to terminate unilaterally a ban on the disposal of low and intermediate level radioactive waste,' says the leaked document. And if other nations insist on an outright ban on nuclear dumping, 'we shall have to say that the UK will be unable to sign the convention as it stands'.
The papers also show that the UK will resist any calls for bigger cuts in pollution and tighter timetables beyond those already agreed.
Greenpeace's marine pollution campaigner Tim Birch said: 'The UK Government is prepared to destroy a new convention to protect the seas of northern Europe so it can carry on using the sea as its own private garbage dump.'
Michael Howard, Secretary of State for the Environment, yesterday said such extremist language was to be expected from Greenpeace. He would not comment directly on the leaked document, but said Britain had no plans to dump nuclear waste at sea and favoured a moratorium.