Addressing HNS members in the "Vatroslav Lisinski" concert hall, Milanovic said he believed that in a year's time Croatia would be based on the leftist and liberal values promoted by the SDP and the HNS.
Peasant Party (HSS) leader Josip Friscic, who was also attending the convention, said he hoped that the HSS and the HNS would contribute to Croatia's prosperity as parties of the centre.
The party convention was attended for the first time by Party of Rights (HSP) leader Anto Djapic, who said that the invitation to attend the convention proved that relations between the two parties had improved and that both parties were more mature than five years ago.
He added that the HSP intended to win the third place in the upcoming parliamentary elections.
The convention was also addressed by senior officials of the Social-Liberal Party (HSLS), the Independent Democratic Serb Party (SDSS) and the Democratic Centre (DC), as well as by representatives of the Primorje-Gorski Kotar Alliance (PGS) and ethnic minorities in the parliament. In attendance were also officials of Liberal parties from Bosnia-Herzegovina and Kosovo, as well as ambassadors and trade union leaders.
The convention is also to be addressed by HNS leader Vesna Pusic and the party's candidate for prime minister, Radimir Cacic.