Many leading scientific research companies are based in Switzerland, and the referendum has caused widespread debate.

Left-wing parties have joined environmentalists and animal rights activists in pressing for a ban, accusing genetic researchers of tampering with nature without clear medical benefits.

But the Swiss government says a ban would hamper efforts to cure cancer and Aids, and result in specialised research jobs going to other countries.

It is the first nation in the world to put the issue of genetic research to a ballot.

Voters were asked to decide whether more stringent restrictions should be placed on scientists.

Consumers are concerned about the safety of food with genetically engineered ingredients

If approved, the new law will ban all research with genetically modified animals and crops. It would also forbid patents for genetically altered plants or animals.

Both consumer and religious groups have expressed concerned about the pace of scientific research.

But opponents of restrictions say the proposed changes will have far-reaching implications for the country's future as a biomedical research centre.

Early indications are that the proposals will be rejected.

The first exit polls broadcast on television show nearly 70% are coming out against the curbs, figures which are reflected in the results already in in nine cantons across the country.

It appears voters in German, French and Italian-speaking areas have not been swayed by the arguments of the environmental coalition.