Swiss voters are going to the polls on Sunday to decide on a government proposal to permit research on the stem cells of human embryos.

Nationwide referendums are common in Switzerland, where nearly every major issue is decided this way.

This ballot makes Switzerland the first country in the world to put the controversial issue to a popular vote.

Scientists believe stem cells may hold the key to treatments for illnesses including Parkinson's and diabetes.

But Switzerland, which is a world leader in medical and pharmaceutical research, has so far not permitted research on human embryos.

For and against

The Swiss government, the universities and the pharmaceutical industry are all urging support for embryonic stem cell research.

They say Switzerland, with its long tradition of medical research, should not be left out of such potentially ground-breaking work.

But the Catholic Church, Switzerland's influential Green Party and medical ethics groups oppose the new law.

Many say the claim that stem cell research could bring cures for illnesses is offering false hope to sufferers, and they suggest cloning will be Switzerland's next step.

In fact, the proposals are strict. Research would be permitted only on cells from embryos less than seven days old which were left over from fertilisation treatment and due for destruction anyway.

Other countries such as Britain and Sweden already have much more relaxed laws, but opinion polls show Swiss voters are divided.

For many, research into human embryos is about more than science and economics.

It raises profound questions about the best way to value human life.