Non-governmental organisations and the Green Party are challenging a decision by parliament to limit the number of non-European foreigners in Switzerland.
They formally launched a referendum on Thursday against tighter regulations on immigration.
The amended law made an unfair distinction between nationals from European countries and those coming from outside, said Green Party parliamentarian Ueli Leuenberger in Bern.
He said about 280,000 foreigners from countries outside the European Union and the three member states of the European Free Trade Association (Efta) would be treated as outcasts.
Leuneberger said the new regulations were the brainchild of the rightwing Swiss People's Party which had succeeded in convincing the centre-right parties in parliament to follow suit.
Slap in the face
Claudio Micheloni of the Forum for the Integration of Migrants (Fimm) criticised the regulations as a slap in the face for hundreds of thousands of foreigners who tried their best to integrate into Swiss society.
He said integration depended on mutual respect between the Swiss and foreigners.
Micheloni also criticised the authorities for trying to impose compulsory language courses for those applying for a residence permit.
He said knowledge of local Swiss languages should not be the main criterion for integration.
The groups now have three months to collect at least 50,000 signatures to force a nationwide vote on the issue.
The new law reaffirms the current two-tier immigration practices which give priority to citizens from Europe's two main trading blocs and highly-skilled labour from outside the EU and Efta zones.
Foreign nationals will no longer be granted permanent resident status automatically after ten years in Switzerland. Families will also find it harder to be united in Switzerland.
On Wednesday an alliance of church groups, aid agencies, refugee and human rights organisations announced plans to challenge the tougher laws on asylum seekers.
The move is in line with a plan by the centre-left Social Democrats, one of the four parties in the Swiss government.
swissinfo with agencies
Parliament earlier this month adopted the law on foreign nationals aimed at tightening regulations on immigration and resident status in Switzerland.
Under the new law foreigners from EU and Efta (Norway, Iceland, Liechtenstein) countries will have priority, while the number of immigrants from other countries is effectively limited to qualified workers.
It will also introduce tougher rules for immigrants to bring their families to Switzerland.
A bilateral treaty between Brussels and the Swiss authorities defines immigration to Switzerland for EU citizens.
At the end of 2003, there were approximately 1.5 million foreigners living in Switzerland, or around 20% of the population.
54% were citizens of the EU or Efta nationals.
42% were immigrants from other parts of the world.
4% of the foreign population is made up of asylum seekers.