Pierre Rusconi with the controversial poster
Reuters
About 60 posters went up in the southern canton of Tessin, which borders Italy, criticising the presence of 40,000 Italian workers and "foreign criminals", according to an accompanying website. Underneath the rats is the word 'Balairatt', which means 'rats dance'.
The posters appeared on Monday, but for days nobody claimed responsibility, prompting speculation the campaign could be the work of a smaller political party or even a businessman seeking to promote Swiss cheese.
"It's a campaign about the things the people in the canton are suffering from," said Pierre Rusconi, the local leader of the party. He added that the party had remained silent during the controversy because "nobody would be interested in the adverts if the (party) had given its name".