Former MP Richard Prebble says he doubts the public will want a return to the First Past the Post electoral system.
Referendums are to be held on the MMP voting system at the next two general elections.
If a majority wants MMP scrapped in 2011, a second referendum will be held in 2014, giving people a choice between the current system and the most popular alternative.
Results of the second referendum will be binding.
Mr Prebble, who served in Parliament under both systems, says voters will likely keep the current one.
Mr Prebble led the ACT Party into Parliament during the first MMP election in 1996.
He says the party would not have had such a significant role in politics if the system had not changed.
The Elections NZ website says previous referendums on proportional representation were held in 1992 and 1993.
They followed a Royal Commission on the Electoral System which recommended in 1986 that New Zealand adopt the German MMP system.
The first MMP election was held in 1996.