National appears likely to offer voters a referendum on MMP.
Leader John Key says his party's election platform was likely to include a two-stage MMP referendum.
Mr Key said voters wanted to think about MMP and have the chance to reassess the voting system.
The referendum news comes as the latest political poll puts the party on track for a landslide election win, with a 27-point advantage over Labour.
The poll, which gave National 56 per cent support and Labour just 29 per cent, would give the party a 13-seat majority.
MMP was introduced in 1996 after a two-stage referendum and more than a decade of debate.
The first referendum would be at the 2011 election and would ask voters: "Are you satisfied with MMP as a system or would you prefer a change?" If there was a majority for change, the second referendum would offer a run-off between different voting systems.