That is the grim prediction of environmentalists who are already campaigning against so-called Frankenstein foods produced by GM crops.
Superweeds – plants not easily controlled by man or nature - will be the result if genetically modified (GM) oilseed rape pollinated with locally grown produce such as cabbage and turnip, say Friends of the Earth (FE).
"Scientists are concerned that allowing GM oilseed rape to be grown in the UK could lead to herbicide tolerant genes and other traits escaping into the wild plant relatives," the group said in a statement.
FE has stepped up its campaign against GM crops as national concern over the issue peaks ahead of a UK government decision on whether to commercialise production.
Danger area map
The environmental lobbyists claim they have mapped out key areas across the UK most at risk from pollen carried from modified rapeseed.
"The long-term consequences of this are difficult to predict. The Government must not allow the biotech industry to experiment with the UK's environment," spokesman Pete Riley said.
The mapping shows areas at risk are regions where five of the GM crop's most closely related wild relatives have cross pollinated with rapeseed in the past.
"Allowing GM oil seed rape to be commercially grown in the UK will almost certainly lead to GM contamination," it said.
GM pollen can be carried by the wind, bees and through human contact over vast distances, the group added.