The changes would make it clear the GCSB could undertake activities on behalf of other agencies including the SIS, police and Defence, "where those agencies can lawfully undertake those activities''.
"This includes the other agencies' lawful investigations of New Zealanders.''
But Mr Shearer this morning said Mr Key's comments about weapons of mass destruction were an attempt to "sex up his policy to push through legislation in a hurry''.
"I think this is weapons of mass distraction by Mr Key. Frankly our GCSB has always been working on cyber threats and that will continue. The question is not about that, the question is about GCSB spying on New Zealanders.''
Labour wants a full independent inquiry into the GCSB and other intelligence agencies before any law changes, rather than what Mr Shearer described as ``a band aid rushed approach based on one report rather than an inquiry.
"What's he got to hide?''
Mr Shearer said that should Mr Key pass the law changes through without the inquiry he was seeking, Labour would hold one when it next got into government.
Mr Key this morning confirmed that as minister responsible for New Zealand's intelligence agencies he had signed an SIS warrant in relation to attempts to obtain science and technology from individuals in New Zealand related to the production of weapons of mass destruction.
Mr Key said he was happy to give Labour and the Greens a briefing on the WMD issue he'd raised yesterday when he briefed them on his law changes.
"The Greens have been arguing from what I can see for better oversight, Labour have been arguing that whatever they did in their time was legal. That's now at least now questionable because of the Solicitor-General's ruling. We're essentially fixing both of those issues. So if they weren't really playing political games I would have thought they would support these changes.''
However, he didn't expect they could be persuaded to support his legislation.
"They're not serious. They're acting like a bunch of kids.''
Mr Key's law changes were prompted by Cabinet Secretary Rebecca Kitteridge's GCSB report last week. It found the bureau may have acted unlawfully when it spied on 88 New Zealanders over the past decade when assisting the SIS and police.
He also unveiled plans to boost oversight of New Zealand's intelligence agencies by beefing up the responsibilities, capability and reporting requirements of the Inspector of Intelligence and Security.
He said Inspector Paul Neazor had decided not to seek another term.
Oversight of intelligence agencies would also be improved through public reporting by Parliament's intelligence and security committee which is made up of party leaders.
Mr Key said he would brief those leaders on the changes this week.
The GCSB's assistance to the SIS and police, which has been on hold since it emerged the bureau had been spying illegally on German internet entrepreneur Kim Dotcom, would only resume when the legislation was passed in the second half of the year.
Other work included changes to legislation around telecommunications interception and network security, to be announced this week.
Mr Key confirmed an investigation into how Ms Kitteridge's report was leaked to the media would go ahead and would be led by former top public servant David Henry.
