A variety of sources to help you with this minefield:
biotechnology and biological sciences research council links to gm technology and use in agriculture

The following sites, Gene tech info service challenged, Monsanto, Iceland Frozen Foods (go through Corporate Information: Our Philosophy) may provide insights that you can usefully input into your research.

You may also wish to think about pesticide use, farming practice and world food security in your endeavour to synthesize some sort of answer.