More than $52 million has been donated to political parties since 1996 by major donors whose contributions are above the threshold for public declaration.
A BusinessDesk analysis of donations found they have come from 538 individuals, businesses, trusts and non-profit organisations.
The average donation is about $47,000, according to the new Cash for Candidates series.
The National party has been the biggest beneficiary, accounting for 28 per cent of total donations, or $14.4m.
Labour has taken in $9.2m and Act $6.1m.