Critics said the posters for tougher rules had racist undertones.
Voters in Switzerland have rejected a move to make it even harder for foreigners to obtain citizenship.
In a referendum, they voted 64% against a bid to revive the practice of approving citizenship candidates by secret ballot and scrapping appeals.
Secret ballots were outlawed five years ago by the supreme court, which judged them to be discriminatory.
Switzerland has one of Europe's highest numbers of foreign-born residents - more than 20%.
Many Swiss said not allowing voters to have the final say on who became a citizen violated the country's system of direct democracy, the BBC's Imogen Foulkes reports from Berne.
However, opponents of Sunday's poll, which was called by the nationalist Swiss People's Party, suspect the real agenda behind it was not Swiss democracy, but how best to keep certain groups out of Switzerland, our correspondent adds.
Twelve years of residence
Initial reporting of the poll results showed that the measure to raise the threshold for citizenship was soundly defeated, gaining approval in only one of Switzerland's 26 cantons (states).
Swiss laws on naturalisation are already tough.
Candidates for citizenship must live in Switzerland for at least 12 years, they have to pass tests in one of the official languages of the country, and culture, and those born in Switzerland have no automatic right to citizenship.
The final hurdle is approval by the local community at a town meeting.
The supreme court outlawed secret ballots five years ago after it became clear that some towns were regularly rejecting candidates from the Balkans, Turkey and Africa, while approving those from Western Europe.
It also gave those rejected the right to appeal.
The Swiss People's Party, the largest in parliament, wants the secret ballots back and the right to appeal removed.