Whistle-blower Edward Snowden has told New Zealanders that they are being "watched" in a mass surveillance.
In the article published on The Intercept, Mr Snowden says he frequently came across communications of New Zealanders while working for the US National Security Agency in Hawaii.
He says that John Key's claim that there were never a mass surveillance of New Zealanders is "false".
"The GCSB, whose operation he is responsible for, is directly involved in untargeted, bulk interception and algorithmic analysis of private communications sent via internet, satellite, radio, and phone networks," he claims.
"It means they have the ability see every website you visit, every text message you send, every call you make, every ticket you purchase, every donation you make, and every book you order online. From 'I'm headed to church' to 'I hate my boss' to 'She's in the hospital,' the GCSB is there."
Mr Snowden says it was possible for the NSA to spy on New Zealanders because the GCSB and NSA share a mass surveillance tool called XKEYSCORE.
"The GCSB provides mass surveillance data into XKEYSCORE. They provide access to the communications of million of New Zealanders to the NSA at facilities such as the GCSB station at Waihopai," he says.
Mr Key has denied that mass surveillance of New Zealanders has ever taken place.