Niue Premier Toke Talagi says New Zealand intelligence agencies have shared information with the country in the past and it would be naive to think it was not subject to spying by other countries.
Mr Talagi said he did not know whether Niue itself was being spied on either by New Zealand or other nations such as China.
"As far as I'm concerned it's part and parcel of what's happening with the world at this moment and I'd be very surprised if there was no surveillance."
He said Niue had received information from New Zealand intelligence agencies in the past.
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One example was last year after American father Jeffrey Hanson, accused of kidnapping his 9-year-old son, sailed to Niue.
Asked about Niue's own intelligence capabilities, Mr Talagi said the "Coconut Wireless Intelligence Service" was in action.
"You laugh, but the coconut wireless is extremely important to intelligence gathering in Niue."
All Cook Islands' citizens are also New Zealanders, but a spokesman for Cook Islands Prime Minister Henry Puna said the issue was not of great concern to Mr Puna at present.