The Scottish Executive has ordered an investigation into the breach.

And Environment Minister Ross Finnie is demanding assurances before he will allow the next farm scale trials to go ahead in the autumn.

I have instructed my GM Inspectorate to investigate in full the nature of this breach with a view to providing a report for the procurator fiscal

Ross Finnie Environment Minister

The initial discovery of the unauthorised GM oilseed rape material was made following a routine audit by inspectors at a Scottish Agricultural College site near Aberdeen.

It was found that 3% of the oilseed rape plants contained a slightly different genetic structure to the one authorised for the trials.

This turned out to be an earlier GM version that is licensed.

The executive said that although the rapeseed posed no threat to human health or the environment, it was a "serious breach" of GM regulations.

The contamination occurred on two Scottish fields and a further 12 in England, where the spoiled crops will be harvested and destroyed.

Sampling regime

The firm which supplied the rapeseed, Aventis CropScience Ltd, could now face legal action.

Mr Finnie said: "I have instructed my GM Inspectorate to investigate in full the nature of this breach with a view to providing a report for the procurator fiscal.

"As a matter of urgency a sampling regime will need to be put in place before the farm scale trials proposed for this autumn go ahead.

This is another fine mess of Ross Finnie's own making

Bruce Crawford SNP environment spokesman

"I have also demanded assurances from Aventis concerning the quality control procedures used in their seed production process and the purity of their seed.

"Again I will need to be fully satisfied on both points before the proposed autumn trials go ahead."

Aventis said it was confident that an improved quality control process would be able to meet any conditions imposed by the Scottish Executive.

However, the company accepted that the trials should not go ahead in the autumn if it could not reach that standard.

Campaign group Highlands and Islands GM Concern called for all crop trials to be halted.

'Massive failure'

Chairman Dr Kenny Taylor said: "The extent of this error beggars belief.

"It shows a massive failure of both company procedures and government regulation.

"This shows that we trust self-policing in biotech companies at our peril."

Scottish National Party environment spokesman Bruce Crawford added: "This is another fine mess of Ross Finnie's own making and could have been prevented if he had listened to the many warnings about the dangers of GM crop trials."