A statement rejecting the agreement on constitutional changes was signed by the deputy speaker of the House of Representatives, Martin Raguz, who had earlier been expelled from the HDZ B-H, the head of the Club of Croat Deputies, Vinko Zoric, Ruza Sopta, Filip Andric and independent MP Ivo Lozancic.
Vlatka Komsic is the only HDZ deputy who did not sign the statement.
The statement said that adoption of the proposed constitutional changes, which were supported by HDZ B-H president Dragan Covic and member of the Bosnian Presidency Ivo Miro Jovic, would have "unfathomable negative consequences for the position of the Croats in Bosnia-Herzegovina."
"We will work on a platform of protecting the interests of the Croat people in Bosnia-Herzegovina and building a democratic, functional and European-oriented Bosnia-Herzegovina with equal individual and collective rights," the five Croat deputies said.
They said they viewed a statement issued earlier this week by Bosnian Roman Catholic bishops, in which the bishops opposed the proposed changes to the country's constitution, as support for their position.
The move by the Croat deputies could have serious consequences for the efforts by seven political parties who discussed the constitutional changes to ensure the necessary majority in parliament for the adoption of the constitutional amendments.
The Bosnian constitution can be changed only by a two-thirds majority of deputies in attendance in the House of Representatives, which will be impossible without the votes of the Croat deputies.