The oil company angrily denied earlier press reports that the Royal Navy had advised it to dismantle part of the pipeline and detonate the bomb where it lay. Enterprise also denied it was risking a large oil spill.
Ron Davie, acting general manager of Enterprise Oil, said: "As soon as we discovered the bomb we approached the Royal Navy and a number of other organisations for advice. They never advised us to dismantle any of the pipeline, and said that exploding the bomb on the spot would be more dangerous than moving it."
The company also said that even though there was minimal risk to the pipeline, it would be filled with water while the bomb was detonated, dispelling any risk of an oil spillage.
A private contractor will move the bomb, which is lying in more than 100 metres of water and some 8 kilometres from its Nelson oil platform, using a remotely controlled submersible operated from a specially modified ship. "The Navy told us 100 metres down in cold water is the safest place for the bomb," Mr Davie added.
Enterprise said the 160,000 barrel-a-day oilfield would be closed for up to five days in an operation expected to take place in the next few weeks. Mr Davie insisted the Navy had advised him the bomb represented only a "minimal risk".
The bomb was detected during a routine annual survey of the pipeline, three kilometres from British Petroleum's Forties field Echo platform. The area is the biggest producer of oil in the North Sea, and lies between Aberdeen and Scandanavia.
The company said it presumed a trawler had dragged the bomb along the sea bed, since there was no seaweed on its casing. Many bombs were ditched in the sea during the Second World War by German bombers either aborting missions or returning from unsuccessful attacks on cities. Many are encountered on the sea floor by companies laying cables and pipelines, Enterprise said.
The Nelson platform supplies crude as part of the Forties network to Cruden Bay in Scotland. Enterprise said the operation will have no impact on crude supplies from other fields using the Forties system.