Labour leader Andrew Little says he wants the Greens and New Zealand First to be represented on the powerful Intelligence and Security Committee.
He also says ministers with any responsibility for spying agencies should not chair the committee, and suggested he could head the panel.
Parliament will this week debate major reforms to spying legislation.
Labour will support the bill at the first hurdle but wants changes if it is to support it further.
In particular, the party wants a narrower definition of "national security" in the Bill, restrictions on the immunity given to spies, and greater protection for private information.
Little also said this morning that he wanted any political party with more than two MPs to be represented on the Intelligence and Security Committee (ISC), which has oversight of New Zealand's spying agencies and operations.
A review by Sir Michael Cullen and Dame Patsy Reddy, which led to the reforms, recommended an expansion of the committee from five to seven MPs.
Little said he wanted two spots on the committee for Labour, one for the Greens and one for New Zealand First - meaning the committee would be expanded to nine members.
The committee should also be headed by an MP who was not responsible for spies, he said, noting that similar committees overseas had been led by an Opposition MP.
Prime Minister John Key heads the committee.
Key said today that the five-person panel had worked "really well" but he was open to a seven-person committee.
However, he questioned whether the Greens would be a constructive member.
"I think the question ultimately for the Labour Party, if they want to put the Greens on the committee, is do the Greens actually believe in the agencies?
"Because if you're just philosophically opposed - that's a legitimate position for a political party to hold - but you're not a very constructive member of the ISC."
Key said the committee's business was highly confidential, but did not go as far as saying the Greens could not be trusted.
It was important that the ISC engaged in useful discussion and not political debate, he said.
The makeup of the committee has led to tension between Labour and Greens in the past.
In the last Parliamentary term, Labour gave one of its positions to former Green co-leader Russel Norman.
After the election, Labour chose to give his spot to David Shearer, saying it needed someone with relevant skills and experience.
The Greens said at the time that Labour had broken the law by failing to consult with other Opposition parties on its selection.