[T]he Opposition [Conservative Party] have consistently resisted, from the time when they were in office until now, any extension of British control over oil in the North Sea. ... The development of the North Sea is going on apace. But we believe that it is right that the British people should have a growing share in the benefits of the North Sea. ... It passes my understanding why a party which used to pretend to speak for the national interest should regularly denounce any extension of British control and ownership of the oil in the continental shelf.