If approved, the proposals would force the Swiss government to place a blanket ban on the cultivation of any plant or import of any animal whose genes had been altered in the laboratory. This would give the alpine nation one of the most stringent regimes governing the use of genetically modified material in Europe, tougher than the restrictions in place in the 25-nation bloc which surrounds independent Switzerland.

Within the EU, restrictions are for specific crops only and temporary in nature, rather than the blanket ban proposed by Swiss ecologists and consumer groups. The proposal is supported by Swiss farmers, many of whom are looking at switching into the booming organic farming business amid moves to slash traditional agricultural subsidies.

Around a quarter of Switzerland's land is given over to farming and around 4.1 percent of the population are involved in agriculture -- roughly the same as in Europe.

A GMO-free zone in Switzerland would be far removed from the mass-production methods used elsewhere, which GMO opponents say disturb the natural balance.

"In the US, where agro-gene technology is used, the environment and nature suffer from monoculture," the supporters said in their proposals to Swiss voters.

The Swiss electorate are regularly given the vote on major decisions under the Swiss legislative system.

However, while the vote has a symbolic meaning, it may mean very little in practice, opponents say.

They argue that a 2004 ruling on GMOs already goes a long way by preventing the use of genetically modified livestock and subjecting GMO plants to a range of tests.

Agro-technology company Syngenta, the world's third biggest producer of GMO seeds, said the measure -- if approved -- would have little economic effect.

Scientists worry that a yes vote would send the wrong signal, however, about research in Switzerland.