The government has denied claims that it attempted to cover up a report questioning the future of genetically modified crops.

The study, published on Christmas Eve, found that the wild turnip weed was affected by gene flow when next to genetically modified oilseed rape, which it is feared could lead to its resistance to herbicides.

Friends of the Earth has claimed that the report warns of the possible development of "superweeds," which cannot be killed through current methods.

Speaking on the BBC Radio 4 Today programme on Monday, environment minister Michael Meacher denied that the report's release date was deliberate.

"We weren't trying to bury it," he said.

"I entirely agree that the Christmas Eve timing was unfortunate...I can assure you there is no wish to conceal. It is another case of cock-up rather than conspiracy."

He also denied that any new evidence had come to light in the report.

"The fact is this information has been known since the early 1990s," he argued.

"These findings are not new, they simply confirm what was already known."

The final results of the study, by Farm Scale Evaluations and commissioned by the Department for the Environment, Food and Rural Affairs, are expected in 2004.