Voters will have to vote twice in separate referendums to get rid of the MMP electoral system, under a schedule revealed yesterday by Justice Minister Simon Power.

The system will be the subject of referendums at the 2011 and 2014 elections.

And if the second referendum decided to replace MMP with another system, the new electoral system would not begin until the 2017 election.

A referendum will be held with the 2011 election asking if voters want change or not and if so, to what system.

If a majority of voters participating in the referendum support MMP, there will be no further referendum.

The Cabinet has not yet decided which alternatives to offer in 2011 or how many options to offer.

But the first-past-the post and supplementary member systems are likely to be among them.

Supplementary member was the least popular option in the 1992 election but Prime Minister John Key has expressed a preference for it.

Under it, only a small portion of the parliament would be elected proportionally.

Mr Key said yesterday National would not have a preferred system.

He believed New Zealanders would not want to return to first past the post.

"My view has always been it is unlikely that New Zealanders will go back to first past the post, but it is always quite a delicate debate so you never really know.

He believed that people were now used to having two votes and saw advantages in it.

"That's not to say the system is perfect and I think from time to time MMP has caused real frustration."

Mr Power briefed other political parties yesterday, and said that while he was open to suggestions from them, the Cabinet would make the final decision.

Legislation required to set up the first referendum will be introduced early next year. Public submissions on the process and questions will be heard by a select committee.

Mr Power said an independent panel would be appointed to conduct a public education campaign in the lead-up to the referendum with a budget of $6 million.The referendum would cost $11.5 million.

The model closely follows the process under which MMP (mixed member proportional) was introduced.

As well as the electoral system, other constitutional issues will be discussed in a review under the supply and confidence agreement between National and the Maori Party.

These could include the term and size of Parliament, the Maori electoral option, and the Maori seats.

Labour and the Greens welcomed the referendum yesterday, although the Greens think the referendum questions should be written by an independent body.

The chief opponent of MMP in the 1993 referendum, businessman Peter Shirtcliffe, said the process could be shortened to one referendum in 2011.

* Referendum on MMP

At the 2011 election:

Voters will have two questions.

- asking they want to keep MMP or change it.

- asking which from a set of alternatives [ yet to be decided] they would support if it is changed.

Independent education panel will spend $6 millionAT 2014 ELECTIONTo be held only if a majority in 2011 vote for change.

One question: which electoral system do you support: MMP or [the highest polling alternative in 2011]?

Independent education panel would spend $ 6 million.TO BE DECIDEDWhat alternatives voting systems to MMP will be offered at 2011.

Who will sit on the independent education panel.

Whether spending limits will be set for referendum campaigning.

* The history

A Royal Commission into the electoral system was set up under the fourth Labour Government, and reported in 1986.

It recommended a referendum on the adoption of MMP (mixed member proportional).

National leader Jim Bolger promised to hold a referendum if National was elected, which it was in 1990.

In a referendum in 1992, 84.7 per cent voted for change and 15.3 per cent g to retain first-past the post.

Of the four alternatives offered, MMP polled highest with 70.5 per cent; then STV (single transferable vote) with 17.4 per cent; PV (preferential voting) 6.6 per cent; and SM (supplementary member) 5.6 per cent.

A referendum was held between MMP and first-past the post at the same time as the 1993 general election and won 53.85 per cent of the vote compared with 46.14 per cent for first-past-the-post.

The first MMP election was held in 1996 and there have now been five Parliaments elected under MMP elections.

A cross-party select committee reviewed MMP in 2001.

In last year's election campaign, National promised a referendum on MMP.