New Zealand First leader Winston Peters today released Mr Key's response to a written question about what his office knew of Dotcom's Overseas Investment Office application to buy the mansion.
In a written answer, Mr Key said then-Justice Minister Simon Power's office phoned a member of his staff last July to say the application had been declined.
"This information was not conveyed to me as it was routine," Mr Key said.
It is understood the staff member who took the call last July was Mr Key's former deputy chief of staff Phil de Joux.
Mr Peters today said Mr Key's written reply suggested he knew of Dotcom much earlier than January 19, 2012 - the date Mr Key has said he first became aware of the Megaupload founder.
"His senior ministers knew of Dotcom, his Helensville electorate office knew of Dotcom, and now it emerges that the Prime Minister's office also knew of Dotcom," he said.
"Mr Key's involvement in the whole fiasco stinks like a sweaty Hobbit's armpit in summer."
A spokeswoman for Mr Key said the written answer was "nothing new".
"The Prime Minister's office answered media queries regarding this in February this year."
