Lobby groups will be able to spend any amount on campaigning in the next general election, the Government has decided.

Justice Minister Simon Power has just announced changes to the laws governing campaign spending during elections, and details of next year’s referendum on the MMP electoral system.

Under the changes, people who spend more than $12,000 on parallel campaigning will have to register with the Electoral Commission. The register will be publicly available.

But unlike under the previous Electoral Finance Act, which was repealed by National last year, parallel campaigners such as unions - or the Exclusive Brethren - will not be limited to spending $120,000 during the campaign.

Political party spending limits are also to be increased, by the rate of inflation from the next election. Currently they are only able to spend $2.4 million if they contest all electorates.

But the Government has rejected proposals that would have allowed third parties to advertise on television or radio during campaigns, plus recommendations that the pool of state-allocated funds available to parties to broadcast advertisements be opened up to newspapers or digital media.

Mr Power said this morning that he could not get sufficient political cross-party support for changes to the broadcasting regime.

"This package comes after extended consultation with all parliamentary parties and the public. As a result the Cabinet has decided to progress reforms only where there is broad public and political support," Mr Power said.

"If we are to have a system which is fair, workable, enduring, and in place before the 2011 election, broad consensus was essential."

In other changes, the Government will modernise the definition of what counts as election advertising and require the Electoral Commission to issue guidance.

The regulated campaign period before an election will be three months before polling day.

The donations regime has been left unchanged, although parties will have to disclose their donations in bands.

Anonymous donations are limited to $1000, and parties must make immediate disclosure of any donation over $20,000.

Meanwhile, Mr Power has also released details of a referendum on MMP to be held at the same time as the 2011 election.

The first part of the proposed question will ask voters whether they want to retain MMP or change to another system.

Part B will ask if there was a change which system should replace MMP.

The options will be first past the post, preferential voting, single transferable vote and supplementary member.

If there is a majority for change, a second referendum will see a run-off in 2014 between MMP and the preferred alternative.

"If there is support to retain MMP as a voting system, there will be a review to see how MMP can be improved,” he said.

Mr Power said the Electoral Commission will undertake an information campaign.

The estimated cost of the referendum, including the information campaign, is $10.97 million.

Legislation is expected to be in place before the 2011 election.