A far-right group campaigning for a change in Croatian election laws says it has collected enough signatures to call a referendum that could curb the rights of ethnic minorities.

The "People Decide" group said Thursday it has collected nearly 400,000 signatures for the plebiscite intended to reduce the number of lawmakers in Croatia's parliament from 150 to a maximum 120, curb the number of MPs representing ethnic minorities and ban them from voting on crucial issues such as forming Croatia's government and the national budget.

The potential referendum has triggered criticism from rights groups and left-leaning parties which say that restricting the rights of minority lawmakers would be against the constitution and the basic principles of parliamentary democracy. Serbs are the largest minority in Croatia.