Protesters in a field of GM crops in Sealand

Yvonne Davies, 45, from Carmarthen, was among a group of 30 people who trampled through the GM maize experiment at Sealand in Flintshire, pulling up plants.

She said she was defending the environment and acting in the public interest.

But on Wednesday, a judge fined the group a total �1,150, suggesting they were serial agitators and said they had undermined genuine environmentalists' cause.

Experiment

The sabotage happened in July 2001 at John Cottle's 10-acre Birchenfield Farm which was hosting a UK Government-funded trial for Aventis Crop Sciences in Wales' second such experiment.

A plea to the farmer to stop participating had failed and a splinter group ignored a large police presence, including a helicopter, to break in to the field where they "went wild", the court heard.

Between one and two-and-a-half acres of the GM crop were destroyed and about a quarter of an acre of conventional crops.

The prosecution said it was difficult to quantify how much the damage was worth.

Fined �400, Davies of Carmarthen, admitted damaging the crop.

People in the street do not want GM crops - I don't regret what I did at all Yvonne Davies

But she denied criminal damage, claiming she acted lawfully because the group were protecting the environment and neighbouring fields from contamination.

The defendants said the tests were flawed and there was no scientific proof that they were safe.

Supporters in the court's public gallery offered to pay her fine.

Davies said: "People in the street do not want GM crops.

"I don't regret what I did at all. I thought we had a very good case to show that we had a lawful excuse for what we had done.

"We have been campaigning for more than four years. I would not have done it if I had not thought that there were thousands of people out there who feel the same way."