"Prove it's unsafe"

UK Environment minister Phil Woolas has supposedly claimed it's now up to the opponents of GM to prove that it is unsafe. This seems like fairly disingenious phrasing -- either it has been proven safe or it hasn't. If it has, then surely that's what he should focus on. If it hasn't, then effectively saying "well, we're stumped; let's put the burden on proving there's going to be a problem" doesn't sound like a sensible approach. It was very difficult to definitively prove there would be a problem with feeding processed cow-remains to living cows (we can kill all the bacteria and viruses), until the BSE crisis hit (oops, we forgot about prions).