Planting GM crops in Britain cannot be justified by the Government trials now being conducted into them, a devastating official report will conclude tomorrow.

The report -- compiled by representatives of the GM industry as well as environmentalists and independent scientists -- will be the biggest setback yet to plans to grow the crops commercially.

It will disappoint Tony Blair by making it virtually impossible for the Government to give the crops a quick go-ahead. The report will also insist that trials should be kept well away from organic farms to avoid contaminating them. This, in effect, backs the Independent on Sunday's campaign this summer to stop a crop trial being held close to Europe's biggest research centre for pesticide-free farming, near Coventry.

The report is the first to be produced by the Agriculture and Environment Biotechnology Commission, set up by the Government last year to provide "independent strategic advice" on GM issues.

The Government has long suggested that the trials, due to end next year, would provide the crucial information for it to decide whether to allow GM crops to be grown commercially in Britain. The industry has long been pressing for this go-ahead, and Mr Blair has long supported it.

But the report says it is "clear" that the trials -- which only look at the effects of the uses of pesticides on the crops, and not at the risks they themselves may pose -- are not sufficient to enable the decision to be made. It says: "They cannot be, as is widely interpreted, the final piece of the jigsaw before commercialisation can proceed."