Prime Minister John Key denies the Government is running a smear campaign against the Labour Party and its leader David Cunliffe over its interactions with businessman Donghua Liu.
It emerged this week that Mr Cunliffe had written to the Immigration Service in 2003 about the businessman's bid for residency, a day after denying he had ever advocated on Liu's behalf.
Mr Cunliffe has accused the Government of giving the letter to media as part of a smear campaign.
John Key told reporters in Washington that Mr Cunliffe and deputy Grant Roberston had "held the blowtorch' to National over the past six months demanding transparency for the New Zealand public.
"All of which is fair enough - we're the Government and we absolutely live to those standards. Now the blowtorch is round the other way, I hope they live to those standards."
Mr Key suggested Labour check their record of donations, repeating claims that Labour's received more than $15,000 from Liu.
Mr Cunliffe said the Labour Party had checked its records and found no donations of any magnitide from the Auckland property developer.
"If the Prime Minister has information then that's a matter that he should put in the public domain. This sort of trial by innuendo I think people are getting very sick of."
Labour MPs say this week's events may have been damaging but the party will get through it.
Veteran MP Annette King said Mr Cunliffe would lead the party's election campaign. She said the MPs need to campaign on the real issues New Zealanders care about, and that Mr Cunliffe will be at the helm.