Ministers should be denied the power to fire advisers who publicly disagree with official policy, under a series of draft principles made public by 28 senior scientists on Friday .

Leading current and former scientific advisers including Lord Rees, president of the Royal Society, and Lord Krebs, former chairman of the Food Stand­ards Agency, called in a document submitted to Gordon Brown, the prime minister, for the freedom to debate publicly and operate without political inter­ference.