The Herald on Sunday newspaper is standing by a story that a Chinese businessman gave the Labour Party $150,000 in donations, including $100,000 for a bottle of wine.
The newspaper says it has a signed statement from Donghua Liu that he paid for the bottle of wine which was signed by Helen Clark at a Labour fund-raiser in 2007, but Labour says it has no record of any donations from Mr Liu.
It earlier reported he paid $15,000 for a book signed by Ms Clark.
Labour Party president Moira Coatsworth said the newspaper is refusing to release the statement, which was signed in May, or to let the party read it.
She said that was a denial of natural justice and the delay in contacting the party about the statement raises serious questions.
But Herald on Sunday editor Miriyana Alexander said it only got a copy of the statement on Saturday and called the party within an hour of receiving it.
Ms Alexander denies there is anything sinister in the timing.
Labour says anyone with evidence of the alleged donations should front up with it now.
General secretary of the Labour Party Tim Barnett said the newspaper told him it was $100,000 for four bottles, not one, but even so, he does not have record of such a transaction.
He said there is still no information on the timing, the venue, or the kind of event at which the claimed payment was made and the party is at an impasse until more information is made available.
Mr Barnett said he had looked through the party's 400 page record of election returns several times without success and had spoken to people who were were around in 2007 when the $100,000 was said to have been paid but no one can provide any information about it.
Labour has also said it has no evidence Mr Liu paid $15,000 in 2007 for a book signed by Ms Clark.
Meanwhile, Labour leader David Cunliffe renewed his claim of a dirty tricks campaign against him when interviewed on TVNZ's Q+A programme on Sunday morning.
"I think you've been around long enough to smell a little bit of set up going on here.
"Now this is a drip feed campaign. What we want to move to is a positive campaign that talks about the issues confronting New Zealanders."
The latest revelation follows Labour accusations that the National Party received donations in return for access to ministers, including from Mr Liu.