Swiss voters firmly rejected on Sunday a far-right initiative that would have made it even harder for foreigners to become naturalised citizens.

Only one of Switzerland's 26 cantons approved the proposal by the nationalist Swiss People's Party (SVP) that would have given local communities the power to decide by a popular vote, which immigrants are granted naturalisation - with no right of appeal.

At present, the decision is made by an ad-hoc commission, usually at the level of the regional cantons.

On a national level, nearly 64 percent of voters opposed the initiative, according to official results carried by the Swiss News Agency.

Switzerland defines nationality by virtue of blood, and those foreigners who wish to acquire citizenship must navigate a lengthy naturalisation procedure, demonstrating a good knowledge of the country's traditions, history and culture - after having lived at least 12 years on Swiss soil.

Children who have one Swiss parent, or the partner of a Swiss citizen, can benefit from a fast-track procedure.

Switzerland's multi-party government - which includes two SVP ministers generally perceived as moderates - was against the nationalist initiative which it deemed arbitrary and discriminatory.

The SVP has long made the question of foreign residents -- who made up a fifth of the Swiss population according to a 2006 census - one of its hobby-horses.

Repeated call for support

Sunday's vote was the sixth time the party has launched a popular referendum on the subject.

The SVP has transformed itself from a small farmers' party into a fiercely populist force with an anti-immigrant message over the past few decades, and scored 29 percent in last October's general elections.

The party drew accusations of racism from a United Nations expert during last year's general election for a poster showing three white sheep kicking a black sheep off the Swiss flag.

This time around it plastered the country with posters showing a sea of black and brown hands grasping for a pile of Swiss passports, with the word "STOP!" in huge letters.

The SVP proposal harked back to a controversial case at the beginning of the decade, when the small commune of Emmen in the eastern canton of Lucerne decided to rule on naturalisation cases by a popular vote.

In 2000, the commune approved eight candidates of Italian origin, but rejected all 48 applications from people from the Balkans.

Switzerland's federal court subsequently ruled that this was discriminatory after the unsuccessful applicants complained. Under the SVP proposals, they would not have this right of appeal.