The development, which comes as the sacked former environment minister Michael Meacher puts himself at the head of the anti-GM campaign, will be seized on by opponents of the technology as undermining its rationale.
It means that bigger quantities of weedkillers - not less, as the biotechnology companies have claimed - will be needed in GM-crop fields, adding to the already intensive agriculture that has wiped out much of Britain's farmland wildlife in the past four decades. Monsanto, the GM market leader, confirmed to The Independent at the weekend that its solution for dealing with resistant weeds was to apply different weedkillers in new ways.
In yesterday's Independent on Sunday, Mr Meacher accused Tony Blair, a GM supporter, of seeking to bury health warnings about GM produce by "rushing to desired conclusions which cannot be scientifically supported".
The revelations about superweeds have been communicated to the Government by an American academic specialising in weed control, who has posted a paper on the website of the official GM science review, led by Professor David King, the Government's chief scientific adviser. This will report soon in advance of a long-delayed decision, due this autumn, on whether GM crops should be commercialised in Britain.