Earlier in the day, Croatia signed the Treaty of Accession with the EU at a ceremony in Brussels.
Lesar told Hina that he would advocate a broad public debate on all aspects of Croatia's admission to the EU.
"We insist that after today's ceremony and before the referendum, a high-quality and broad public discussion be held in Croatia on the content and aspects of EU accession."
At the ceremony in Brussels, the Accession Treaty was signed by 27 EU member-states' leaders and Croatia's President Ivo Josipovic and Prime Minister Jadranka Kosor.