It comes amid speculation that ministers are ready to relax control on the cultivation of GM crops.

BBC: Owen Paterson backs UK-grown genetically modified food

The speculation was that Merck wanted to force concessions out of Bayer, trading control for choice businesses or patents from Bayer or Schering.

ECONOMIST: Two historic German drugs firms scrap for control of a third

The comments fuelled speculation that Mr Portillo had made a deal with Mr Hague to take full control over economic policy before his surprise promotion to the shadow cabinet earlier this month.

BBC: Portillo's pledge on tax