Winston Peters claims the Government co-operated with Fiji's military regime when the SIS "raided" a New Zealand-based member of the Fiji Freedom and Democracy Movement last year.
The NZ First leader says the questioning of former Fiji Cabinet minister Rajesh Singh and the search of his Auckland home by Security Intelligence Service and police personnel took place after the Government received "fictitious" information about an assassination plot aimed at military leader Frank Bainimarama.
Mr Peters first made the allegations in Parliament on Tuesday but yesterday went further, claiming the "raid" in which Mr Singh's computer and a phone were seized was illegal and that the GCSB were involved in spying on Mr Singh and his associates.
Mr Peters asked Prime Minister John Key if the Government had made an arrangement with the Fijian regime to spy on Mr Singh and other members of the Fiji Democracy and Freedom movement living legally in New Zealand.
Replying on behalf of Mr Key, who is attending the Pacific Islands Forum in the Marshall Islands, Deputy Prime Minister Bill English said it would be "very surprising" if the Government made any arrangement with the Fijian Government.
Mr Peters then asked: "Why did the commander of the Fijian Land Forces Colonel Mosese Tikoitoga text Mr Singh saying he was about to be raided by the SIS at the exact time the raid was happening?"
He read out what he said were a series of text messages from Colonel Tikoitoga to Mr Singh in the days following the raid including "Bro you not worth a bullet cause u don't deserve it" and "you will be deported soon for being threat to NZ govt".
Mr Singh later told the Herald Mr Peters' description of what happened including the content of the texts was accurate.
The texts were evidence "of the knowledge of the Fijian Government before the raid happened, as the raid happened, and after the raid happened", Mr Peters told Parliament.
"They leave no doubt that the Fiji dictatorship knew what was happening and had contacts in high places in New Zealand."
He also claimed the SIS breached Section 131 of the Search and Surveillance Act as they did not produce evidence of identity or a search warrant when they raided Mr Singh's home last year.
Mr English denied any unlawful activity by the SIS saying Mr Singh should make a complaint to the Inspector-General of Intelligence and Security or Police if he believed they had acted illegally.
Mr Singh told the Herald he had complained to the Inspector-General last year but never received a response.