It is understood that leaks have been discovered in valves on the manifold at drill centre one at the field, some 90 miles north of Orkney. Five sets of "Christmas tree" valve assemblies are also to be lifted from the seabed causing delays which could cost up to £1.5 million a day.

First oil from Foinaven which will be carried to Flotta by dedicated shuttle tanker from the FPSO Petrogarl Foinaven, was originally due in June 1996 but delays including earlier problems with a manifold have set the project back almost a full year.

The decision to lift the equipment which is in around 500 metres of water, follows extensive hydro-testing of the subsea equipment said BP.

A spokesman for BP Exploration said: "Our commitment to environmentally responsible operations west of Shetland is total. We have decided to recover the manifold from the seabed to fully inspect it and take whatever steps are necessary to give us complete confidence in the system.

"In parallel, and as part of the same programme five Christmas trees will also be retrieved for inspection. This process will take some time to complete and while the delay may be unfortunate, it is secondary to safe and environmentally responsible operations."

As if technical hitches were not enough, environmentalist group Greenpeace are putting the pressure on the Government and Shell, who have a 28 per cent stake in Foinaven to stop exploration in the Atlantic Frontier region.

Greenpeace argue that any exploration of the area covered by the 17th licensing round which includes areas of the Atlantic Frontier would be illegal and irresponsible.

Deputy executive director of Greenpeace. Mr Chris Rose said: "There is no alternative to a phase out of fossil fuels if we are to prevent climate change. Since we cannot burn all that we already have to explore for more oil is not only futile but extraordinarily irresponsible

"The UK Government must stop the oil exploration in the Atlantic Frontier and as Foreign Secretary Robin Cook shouldn't cook the planet but lead an international negotiation for the orderly phase out of fossil fuel."

The call for Shell UK to stop their oil exploration on the grounds of climate change came on the day of their annual general meeting yesterday.

Sarah Burton of Greenpeace said: "Shell tries to present themselves as taking a more environmental or sustainable approach to their work while at the same time blatantly ignoring the impact of their product on the climate".