A new poll indicates support for New Zealand First has reached the 5% threshold required to enter Parliament, despite the controversy over donations surrounding Mr Peters.
The Roy Morgan survey has the National Party at 48%, and Labour at 37%.
Its previous survey had New Zealand First on 2.5% support.
Donations to New Zealand First and to Mr Peters' legal bills are being investigated by the Serious Fraud Office, police and Parliament's privileges committee.
The Green Party is the only other minor party to poll above 5%, with 6.5% support.
823 people were surveyed from 1-14 September.