The veto request was filed yesterday by a group of councillors headed by public sector unionist Branimir Štrukelj.
After its passage last week, public sector unions announced a general strike for 23 January. They labelled the budget implementation law illegal and unconstitutional, saying it encroached on the system of public sector wages and the collective bargaining agreements.
The unions also announced launching a referendum procedure, but they will try to veto the law first.
The unions "will do everything to get the government back to the negotiating table", Štrukelj announced at the time.
The vote comes a day before the new National Council takes over on 12 December. Elections for the 40 seats were held on 21 and 22 November.