Switzerland's citizens vote this weekend on whether to severely restrict genetic engineering, potentially forcing thousands of biomedical researchers abroad and seriously harming university and industrial research.
Polls suggest the yes and no votes are roughly equal with a large percentage of citizens still undecided.
But scientists, who have protested on Zurich's streets, this week warned that a yes vote would force Swiss biomedical research into a third-rate position.
The referendum proposals include a ban on transgenic animals, a ban on field trials of genetically modified plants and the refusal of patents for genetically modified animals and plants.
It demands that scientists demonstrate in advance of their research its value to society and that there are no alternative methods.
The referendum, one of several held annually, is the result of proposals put forward in 1992 by 70 pressure groups opposing biotechnology.
According to Swiss law, any proposal for constitutional amendment that is signed by 100,000 citizens must be put to the vote.
Although widely supported by environmentalists and animal rights activists, the proposals have been staunchly opposed by scientists, pharmaceutical companies and both houses of the Swiss parliament which has instead put forward a package of measures, referred to as the "Gen-Lex" motion, to co-ordinate and more strictly monitor biotechnology, but not to ban it.
According to Rolf Zinkernagel, director of the Institute for Experimental Immunology at the University of Zurich, the outcome of this weekend's referendum is not at all clear. In a recent survey 36 per cent of those polled were for the ban, 38 per cent against, and the remaining quarter undecided.
"A yes vote on Sunday will mean Swiss biomedical research falling off the wagon and becoming third rate," he said. Up to 2,000 researchers and about 500 research projects could be directly affected by a yes vote as individuals and companies move abroad.
More than half of the overall vote, and a majority of the cantons, have to vote in favour of the ban for it to be enacted.
Opinion, page 14