By Kate Chapman of NZPA

Wellington, July 22 NZPA - The public information campaign about the referendum on MMP should be started early next year before people get too distracted by the rugby World Cup, politicians were told today.

Holding the referendum was an election promise from National.

Under the Electoral Referendum Bill voters in the 2011 general election will be asked whether they want to retain MMP and secondly which alternative system they prefer from a list of options. If the vote is for change a run-off between MMP and the most popular option will be held at the same time as the 2014 general election.

If more than 50 percent of voters opt to retain MMP in the first referendum, the Electoral Commission will undertake a review to consider whether changes to it are needed.

Appearing before Parliament's electoral legislation committee today, Campaign for MMP spokeswoman Sandra Grey said a public information campaign was need to tell people what the referendum was about, and how it worked.

She said the campaign should be conducted by an independent body, not the Electoral Commission, which would be too busy preparing for the election itself.

The campaign should also be carefully timed because the election was likely to fall before, or soon after, the rugby World Cup and people would be concentrating on that.

The World Cup runs from September 9 to October 23 in New Zealand next year.

While a public information campaign was needed there should be a cap on advertising for those promoting a particular voting system, Ms Grey said.

Her organisation had reviewed submissions to the committee and found more than 80 percent wanted controls on spending for the referendum.

A limit would create a level playing field, she said.

"Spending caps are necessary to ensure a fair referendum and a result that voters will trust," she said.

Campaign for MMP supports a limit on spending of $350,000 for the referendum but would settle for restricted advertising on television and radio.

"TV and radio are most susceptible to big spending manipulative advertising campaigns."

Advertising would still be possible in newspapers, magazines, billboards and on the internet.

Under such an arrangement information available from broadcasters would be solely from the Electoral Commission.

Canterbury University political scientist Therese Arseneau said it was important the referendum allowed people to express a clear-cut and unequivocal answer.

Clear and simple wording was also important, she said.

"The most effective referenda make it easy for voters to say what they want to say with the simple 'tick'."