GENEVA - Swiss voters Sunday will decide whether to dramatically cut immigration numbers in the name of saving the environment, in a referendum that opponents have labelled xenophobic and disastrous for the economy.
Most voters have already cast their ballots by mail, and initial results should be available shortly after polls close at noon (1100 GMT).
Surveys have shown the so-called Ecopop initiative gaining momentum in recent weeks but still indicate it is doomed to fail.
In the latest opinion poll, 56 per cent said they would nix the proposal which maintains that the current influx of foreigners is swelling the Alpine nation's population and shrinking its idyllic landscapes and green spaces.
Supporters however stress that surveys often underestimate backing for populist initiatives and insist the country could be in for a surprise.
It would not be the first time.
Last February, the approval of an initiative demanding quotas for immigration from the European Union caught many off guard and threw non-member Switzerland's relations with the bloc into turmoil.
'Already too crowded'
Foreign nationals already make up nearly a quarter of Switzerland's eight million inhabitants, official statistics show.
According to Ecopop, immigration is adding 1.1-1.4 per cent annually to the Swiss population, putting the country on track to house up to 12 million people by 2050.
"It's already getting too crowded here," Anita Messere of the Ecopop committee said, arguing that the inhabitable plains of the mountainous country were being covered in concrete at a rate of more than one metre (yard) per second.
The campaign wants to cap immigration growth at 0.2 per cent, or an addition of around 16,000 people annually, which it says would allow the number of inhabitants to increase to just 8.5 million by the middle of the century.
It also wants to help rein in over-population beyond Switzerland's borders, calling for 10 per cent of the country's development aid budget to go to family planning initiatives abroad.
The government, all political parties, employers and unions have rejected the initiative, slammed by some as xenophobic and by others as a threat to Switzerland's economy which depends heavily on immigrant labour.
Christian Luescher, a parliamentarian for the Liberal Party and co-chair of the committee opposing Ecopop, described the initiative as "absolutely absurd".
"It aims to drastically, linearly and arbitrarily reduce immigration to Switzerland, with absolutely no consideration for the needs of the economy," he told AFP, warning it would "impoverish our country".