These reasons are those of the Green group in the EU Parliament, not mine. You can read them here.
This is their shot across the bows of the EU Commission which recently submitted to the EU standing committee on plants, animals, food and feed (which sounds a bit like Ofscoff), three draft regulations aimed at renewal of the authorisation of cultivation within the EU of three GM maize varieties. The Greens don't like the idea.
And here is Mark Lynas's response to all this. Wonderful teaching aids, all. As to where I stand on all this – actually it's right next to Lynas who's not pro- or anti-GM; just pro-science. Just so. And to think that we'll soon be leaving all this behind – well, the EU bit of it.