"I think you should ask the Government how come the Prime Minister had a copy of that letter two weeks earlier when the media put in an OIA on Monday."
Immigration Minister Michael Woodhouse this afternoon confirmed his office had briefed Mr Key's office about the letter within a few days of learning of it on May 9.
"That didn't include sending the Prime Minister's office the letter," Mr Woodhouse said.
"What I notified them of was the existence of the letter. At that point I hadn't even seen the letter myself I was just told it was on file."
Mr Key's office was "made aware of the existence of the letter and the broad contents of it, that he (Mr Cunliffe) had supported a speeding up of the process of the application."
Mr Woodhouse learned of the letter just a day after the Herald requested Immigration NZ's entire file on Liu's residency application.
However, Mr Woodhouse's office said the letter came to his attention when he asked officials for a detailed briefing on Liu as a result of Labour's questions to him about his links with the millionaire property developer.
The Herald's Official Information Act request for Liu's file was declined for privacy reasons but the letter was released when a further request for any material in the file regarding MPs was submitted early this week.
Senior Cabinet Minister and National Government strategist Steven Joyce this afternoon denied any dirty tricks campaign against Mr Cunliffe.
"Mr Cunliffe has been running his own dirty tricks campaign and it seems to be working. He hasn't been telling himself what he's been doing."
Earlier, Mr Cunliffe said Immigration NZ had not told him about the letter or that it was going to release it until half an hour before it was released on Wednesday. "That would have been a courtesy."
Read the letter Cunliffe wrote in support of Donghua Liu here
Mr Cunliffe fronted for media this afternoon alongside MP Grant Robertson in an apparent bid to stem talk of disunity or any challenge on his leadership.
Mr Cunliffe called his front bench team to his office in Parliament to discuss yesterday's developments over the 2003 letter, and afterward fronted for media with Mr Robertson and his deputy David Parker.
Mr Robertson is considered the most likely contender if there is a pre-election move to roll Mr Cunliffe - although Mr Robertson told the Herald this morning he had no intention of doing so.
Asked why Mr Robertson was alongside him, Mr Cunliffe said it was because he was a "highly regarded member of my senior team."
"We are here to answer your questions."
Mr Cunliffe said he had not sought a loyalty affirmation from all his MPs, or from Mr Robertson individually. "I don't need to."
Mr Robertson chipped in at that point: "I am loyal to David Cunliffe." Asked if he still had ambitions to lead the Labour Party, Mr Robertson replied that although he had contested it last year, Mr Cunliffe was the leader and "he won it fair and square."
"After David's had three or four terms as Prime Minister, it could be my turn."
Mr Cunliffe said his meeting with the front bench had been to review the past 24 hours, during which Labour was also hit by a second bad poll - getting just 23 per cent in the Stuff Ipsos poll.
Mr Cunliffe said there were several reasons his staff had not found the 2003 letter when they first checked his records.
They had done a manual search of hard copies, but only kept them for about 3 years. One computer hard drive from his office had been stolen, another was disabled in a power spike, and the letter was mis-filed under LUI rather than LIU in a retired staff member's files.
