The GCSB considered recording Prime Minister John Key's address to staff when he visited the spy agency in February - but decided against it before he arrived.
Mr Key said today that the director of the GCSB had relayed that it had considered recording his speech, in which Labour leader David Shearer alleges the Prime Minister made a joke about Kim Dotcom.
Mr Key maintains he does not remember making the quip and there is no official GCSB recording of his speech.
Mr Key said he was notorious for cracking jokes on topical issues and it would not be out of character if he did so about the Megaupload millionaire during his GCSB visit on February 29.
He said making such joke would not mean he had been briefed about the agency's spying on Dotcom that day.
During a press conference at Auckland airport this afternoon, Mr Key said he made jokes about "everything from water to ACC" as well as Dotcom.
He said he would not cut back on the jokes he made.
"Give me a break. I go out there and speak and entertain thousands and thousands of people every week. I can be straight-laced and completely boring if you want me to be but I don't really see how that's going to do much."
Mr Key said Mr Shearer's claims that the GCSB seized and destroyed footage of the Prime Minister's address to the spy agency in February were driven by "utter desperation".
"He probably should apologise to the GCSB [for making the allegations] with no backing," Mr Key said.
He maintains his first briefing about the spying probe of Dotcom was on September 17.
Mr Shearer said GCSB sources claimed Mr Key joked about the Dotcom case while at the bureau for the February briefing - months before he originally claimed to know the agency was linked to the case.
"I don't recall that," Mr Key said this afternoon.
"I'm notorious for cracking jokes at events that are in the public domain. Mr Dotcom's name had been in the public domain for five weeks [by February 29].
"But there is no recording from the GCSB, there's never been a recording from the GCSB, they've checked when those cameras were used, they've checked with the operators, they've checked the back-up logs."
There have been claims Labour's source in the GCSB is the partner of one of Mr Shearer's staff.
Mr Key said he did not know where the information came from but he called on Mr Shearer to make public any recording he had of the joke if it had been filmed on a private device.
The GCSB took 11 still images of the address but they could not be released because they identified members of the spy agency who needed to remain anonymous, Mr Key said.
John Key on his sense of humour ...
"I'm notorious for cracking jokes"
"To be honest with you I can't remember the jokes I cracked in LA [last week]"
"I often get up and crack jokes about topical events"
"I crack jokes about everything from water to ACC"
"I go out there and speak and entertain thousands and thousands of people week. I can be straight-laced and completely boring if you want me to be but I don't really see how that's going to do much"