New Zealand's allegations aimed to sow suspicion, "poisoning" the two countries' relations, said a spokesperson for the Chinese embassy in Wellington.

"The accusations sound very familiar as they rehash smears and slanders fabricated elsewhere, repackaged for the New Zealand audience," the spokesperson said.

"We have regarded, and are willing to continue to regard New Zealand as a friend and partner. But the healthy and stable development of bilateral relations depends on the joint efforts from both sides."

The New Zealand Security Intelligence Service warned in its annual threat assessment that China was the most active power engaging in foreign interference, including through the use of front organisations.