Beijing has reportedly expressed concern at the claims, which are based on documents from US whistleblower Edward Snowden obtained by Auckland's Herald on Sunday newspaper.
The newspaper reported that New Zealand intelligence and the US National Security Agency collaborated on a plan to hack a data link between China's consulate in Auckland and a nearby visa office run by the Chinese.
It said it was unclear whether the hack went ahead because Snowden fled the NSA in May 2013, before it had come to fruition.
State news agency Xinhua said the Chinese embassy in Wellington issued a statement saying it was concerned about the report and attached great importance to cyber security.
"We will firmly safeguard our security interests and continue to guarantee our cyber and information security with concrete measures," it said.
"At present, cyber space is riddled with chaos and uncertainty. China proposes to settle disputes through dialogue and formulate codes to regulate cyber space behaviours that are acceptable to all sides."
Key refused to comment on the report, saying only that the documents it was based upon had been stolen.
He refused to speculate on whether the issue could damage relations with China, New Zealand's largest trading partner.
"You're asking a hypothetical question and I'm not going to do that because I can't give you an answer, I don't know," he said.
"What I can tell you is we've got an immensely strong relationship with China, it's very open and we talk to them about all sorts of things,
"If they want to raise any issue with us they're welcome to, but I'd be surprised if they do."
New Zealand is part of the "Five Eyes" intelligence network which also includes the United States, Britain, Australia and Canada.
Snowden documents released last month alleged Wellington was conducting mass surveillance on its South Pacific neighbours and passing the information onto its Five Eyes partners.
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