The Forties field, 273 km north east of Aberdeen, is the third biggest single oil producer for BP in Britain but the company said it had lost faith in the tax regime.
The opposition Conservative Party described the move as a vote of no confidence in the government after Gordon Brown raised taxes by 10% on offshore oil and gas fields in the face of deep opposition from BP and the rest of the industry.
BP is selling its 96.14% stake in Forties together with a package of shallow-water assets in the Gulf of Mexico as part of the deal with Apache. Instead, it is concentrating its spending on deep water schemes in the Gulf of Mexico, Angola and elsewhere.
