The Swedish authorities have demanded that the fields, planted on 11 June, be cleared of Amadea, but are allowing the Amflora plants to remain, despite the contamination. They have ordered BASF to account for similar GM potato fields in Germany and the Czech Republic.
Greenpeace EU agriculture policy advisor Stefanie Hundsdorfer said: "This is a deplorable lapse in bio-security. Who knows what the effects of growing a largely untested GM crop for months in the open environment will be? The Swedish authorities should order all plants in the contaminated fields destroyed and BASF should test all Amflora fields and destroy all plants where contamination has occurred.
"Biotech companies have repeatedly mixed up GM with normal seed. They can't be trusted and contamination seems inevitable. European governments must put a stop to the European Commission authorising new GM crops. This is the only way to prevent contamination of our food and fields." 
The episode will be embarrassing to BASF, which invited German Federal Minister of Economics and Technology Rainer Brüderle to a high-profile ceremonial harvesting of Amflora on 31 August. At the same event BASF announced it was requesting permission from the European Commission to grow Amadea, a high-starch potato mainly intended for industrial use.
The Swedish contamination follows an almost identical case in which thousands of hectares of unauthorised GM maize had to be destroyed after being grown illegally across Germany this summer.
Over 750,000 Europeans have signed a petition calling for a moratorium on all new GM crops in the EU until a proper safety regime is put in place by the European Commission . The petition is set to be one of the first to test how serious the Commission is about its flagship engagement policy, the Citizens' Initiative.