Key Points:

Officials were given just two days to come up with details for rules on anonymous political donations - an eleventh hour addition to new electoral finance laws.

A report reveals the haste in which the new law to govern anonymous donations was developed to insert into the controversial Electoral Finance Bill.

The donations regime was not in the original bill, so was not subject to public submissions.

The advice to the justice and electoral select committee shows that, on October 29, the committee explained what it wanted to achieve and asked advisers for a written outline and advice on the "fine-detail" of the regime by November 1.

The report by the Ministry of Justice and Electoral Commission reveals officials were specifically told not to consider any other options to cover anonymous donations.

The report shows the Parliamentary Counsel Office drafted the legislation as it was being considered by the committee.

The Ministry of Justice was then given a further three days - until November 5 - to analyse the draft and provide advice in time "to meet the committee's deadline for consideration of the bill".

The select committee also ignored advice to set the threshold on anonymous donations between $3000 to $5000 - rather than $1000 - to help reduce the compliance costs on both the Electoral Commission and political parties.

Labour and the Green Party have described the rules as a victory for transparent elections, and a way to stop secret money having an influence on politics.

National Party deputy leader Bill English said the bill was developed through "an appalling ad hoc process and patch-up jobs.

"Labour is tinkering with important constitutional laws that go to the heart of our democracy. It should not attempt to railroad this law with a slim majority of Parliament."

He said the bill was so confusing that even Labour did not know what was covered by it.

Justice Minister Annette King said Mr English was mischief-making and that the "law of common sense" would apply in many circumstances.

The new rules require any donations in excess of $1000 to be channelled through the Electoral Commission and limits parties to receiving a maximum of $240,000 in anonymous donations every three-year election cycle.

It effectively ends the days of "secret" trusts by requiring disclosure of who makes donations of more than $1000, unless they are sent through the commission.

The Human Rights Commission has described the revised bill as, effectively, a completely new piece of legislation. It was "disappointed" the addition was not sent out for further public consultation because of its constitutional importance.

But Ms King was unapologetic about the push.

"We have to make some decisions. We are coming into the election year and you could just drag on and on without making decisions about how we run our electoral system. We can't go through another election with some of the things that happened in the last election."

The advisers' reports also show the committee's $120,000 election year spending limit for interest and advocacy groups was less than half of what the Electoral Commission recommended.

The commission set a $250,000 to $300,000 limit based on the real costs of advertising and the need to give groups some leeway for "the existing uncertainty about which 'normal activities' will fall within election activity".

In its report, the select committee said $120,000 was enough to "ensure that third parties could express their political support adequately whilst still meeting the objectives of the expenditure cap regime".

However, the commission said $250,000 could run a nationwide, two-week campaign on an issue, based on the cost of advertising.

The Electoral Commission also recommended a threshold of $40,000 before lobby groups had to register as a third party - higher than the final select committee decision of $12,000. It said $40,000 was the point at which an advertising campaign would begin to register on the wider public radar and people would want to know more about the group than simply authorising name and address.

It was also high enough for small and moderate groups to mount smaller campaigns without worrying about breaching the threshold.

"The intent is to remove compliance costs that will deter small groups from participation in the campaign while ensuring transparency about those groups seeking a substantial voice."