Prime Minister John Key believes the Labour has a lot more than $15,000 in donations from wealthy Chinese political donor Donghua Liu.
He also acknowledged he had known for some weeks that Labour leader David has written a letter supporting Mr Liu's application for residency.
The release of the letter yesterday in the face of denials from Mr Cunliffe that he wrote any such letter has thrown his leadership into crisis.
It followed revelations earlier this week that Mr Liu donated $15,000 to Labour in 2007.
It did not show up in the donations register although that may have been lawful at the time.