The public relations adviser to Owen Glenn says he is unable to confirm whether the expatriate businessman made a donation or loan to the New Zealand First Party.
Mr Glenn was the Labour Party's biggest donor at the 2005 election.
Party leader Winston Peters is demanding an apology from The New Zealand Herald for a report that Mr Glenn admitted in an email to making a donation. He describes the report as a work of fiction.
The email was written to Auckland public relations adviser Steve Fisher who said on Monday that when the matter first arose in February, he advised Mr Glenn to refer all questions to New Zealand First.
Mr Fisher says he no longer has the email, cannot confirm its wording and does not know how it was obtained by the newspaper.
He says he cannot remember if Mr Glenn told him he had given money to the party.
Mr Peters says the party has no records of any loans or donations from Mr Glenn, who is based in Monaco.
Mr Peters says the newspaper's editor and the journalist who wrote the story are welcome to go through the party's accounts.
Mr Peters was questioned about Mr Glenn in February, after then-party president Dail Jones said New Zealand First had received a five-figure anonymous donation.
Mr Peters said at the time that the money was a consolidation of party funds and Mr Jones was mistaken.
But the paper says it stands by its story and the journalist who wrote it.
Editor Tim Murphy says the story was based on explicit emails and Mr Peters' response has left open to interpretation possibilities of funding assistance for New Zealand First and its interests.