Green Party leader Jeanette Fitzsimons has again said she would find it difficult to work with New Zealand First leader Winston Peters in any post-election arrangement.
Labour may need the support of both the Greens and New Zealand First if it has a chance to form a government after the election.
Ms Fitzsimons said the latest claims about Mr Peters and Owen Glenn are just another stage in the donations saga.
Winston Peters on Wednesday denied he pressured officials to appoint the expatriate businessman as honorary consul to Monaco, following the release of official papers suggesting he did so.
Jeanette Fitzsimons said her party believes New Zealand First is unlikely to return to Parliament, as it is currently polling below the 5% threshold.
But she said she would find it difficult to work with Mr Peters while the police investigation continues into donations to his party.
On 23 October the Electoral Commission cleared the party's secretary of any offence in relation to the 2007 return of donations, which the party has since updated to include an $80,000 donation from the Spencer Trust. The commission said the party's returns for the previous two years also had to be updated.
Police said last week they expected to conclude their inquiry into the issue this week.