"The Constitution guarantees equality to all Croatian citizens, who have the same rights and obligations. There can be no first and second-class citizens," Sanader told Hina on Saturday.
Sanader believes that the SDP and Milanovic are sending "destructive messages to a smaller, but definitely not less important part of the Croatian people".
The SDP is trying to question the ruling of the Croatian Constitutional Court which supports equal voting rights for all Croatian citizens, including Croats in Bosnia and Herzegovina, Sanader said.
"As Prime Minister and president of the HDZ, I guarantee that all Croatian citizens will keep their right to vote in elections and referendums," he concluded.
In an interview with the Sarajevo daily Dnevni Avaz that was published on Saturday, SDP leader Zoran Milanovic said that if his party won parliamentary elections later this year it would advocate that the Bosnian Croats be stripped of the right to vote in elections or referendums in Croatia because they are not part of the Croatian diaspora.
"Croats have lived in Bosnia and Herzegovina for over a thousand years, so they're not an emigrant community," Milanovic said.
"They (ethnic Croats) live in Bosnia and Herzegovina and should vote for representative bodies there, but not in Croatia," the SDP leader said, adding that there was no dispute that they should have dual Bosnian and Croatian citizenship, but without the right to vote in Croatia.