At the central ceremony in Zagreb, HNS leader Vesna Pusic said that over the last 15 years Croatia had transformed into a normal democracy, and added that the HNS should continue working on the job it had started 15 years ago.
"The HNS has promoted ideas and positions which have not been always conventional or usual but which have become common in Croatian politics," Pusic told participants in the ceremony.
The HNS honorary president, Savka Dabcevic Kucar, said Croatia was now on an ascending path, adding that challenges which Croatia was now facing were in the focus of the party's activities, notably in the economy and European integration.
The chairman of the HNS main committee, Radimir Cacic, spoke about prominent HNS members Mika Tripalo, Kresimir Dzeba, Srecko Bijelic, Dragutin Haramija and Stjepan Mesic.
Cacic said the party had 27,000 members and 800 representatives in local authorities.
Present at the ceremony were representatives of the SDP, HSS, HSP, HSLS, PGS, DC and SDA parties.
At the start of this year, the HNS and Libra parties merged into one party called the HNS-Liberal Democrats.