Wide breaches of rules to control genetically modified crops have been uncovered in supposedly GM-free Tasmania.

Thousands of regrowth "volunteer" GM canola plants have been found flowering at 11 sites around the State in a Commonwealth audit of fields where crops were previously grown by the agriculture multinationals Aventis and Monsanto.

The breaches came despite a ban in Tasmania on any growth of GM plants in the open. An outraged State Government, which made public the breaches, said it was astonished not only by their number but by the previously unknown scale of the trials.

The Federal Health Department's interim office of the gene technology regulator (IOGTR) confirmed that two weeks ago it began a compliance check on Tasmanian trial sites where GM canola was grown up to three years earlier. When it found "non-compliance issues" it expanded the
check, said the head of the IOGTR, Ms Elizabeth Cain.

According to the Tasmanian Primary Industries Minister, Mr David Llewellyn, the audit found a total of seven sites where a small number of GM plants were still growing, while at four others there were thousands of mature plants growing from seed dropped by the original crops.

Since Tasmania declared GM crops to be prohibited weeds in July, none has been allowed to be grown in the open.  Mr Llewellyn said he was concerned about pollution of Tasmania's
environment that may have occurred with the transfer of GM material into buffer zones around the crops, and particularly into a native wild turnip. He also warned that such a failure to comply with the rules could occur elsewhere.

"I think this might also be the case in other States where this crop is grown," he said.

Ms Cain said the companies' failure to comply with the guidelines posed negligible risk to the environment, and no risk to human health and safety. She said they were given 48 hours to take remedial action.

Asked to categorise the scale of the incident, she said "there are other breaches with GM crops we've regarded as more serious".

Monsanto spokesman Mr Brian Arnst said volunteer plants were found at two of its previous trial crops, one dating from 1999.

An Aventis spokeswoman could not be reached for comment.