A paper to be published in the prestigious scientific journal Nature on 7th October demolishes the key assumption underlying the international safety regulation of GM food. The concept of "substantial equivalence" [1] has formed the basis of many food safety systems around the world (including the UK) but three scientists [2] writing in Nature have condemned this assumption as a 'pseudo-scientific concept' serving the interests of big business. The critique could destabilise America's aggressive stance on GM food and crops at World Trade Organisation negotiations.