A "deeply concerned" China has hit back at a show of unity from Scott Morrison and Jacinda Ardern, saying Australia and New Zealand are guilty of making groundless accusations of human rights abuses.
On Monday, the trans-Tasman PMs met in Queenstown for their annual leaders meeting.
Both Ms Ardern and Mr Morrison refuted persistent criticism New Zealand is cosying up to China and ignoring its human rights record.
In a jointly issued statement, Australia and New Zealand "expressed serious concern over developments in the South China Sea", describing China's militarisation in the region as "destabilising".
They also expressed "deep concern" over Hong Kong's slide towards autocracy and "grave concerns" about human rights breaches in Xinjiang province.
It is there that China stands accused of running torturing and illegally detaining the region's majority Muslim population.
Foreign Affairs spokesperson Wang Wenbin said China took note of the discussions and was deeply unimpressed.
"The leaders of Australia and New Zealand ... have made groundless accusations against China, grossly interfered in China's internal affairs and seriously violated the international law and basic norms governing international relations," he said.
"It's not justifiable for relevant countries to ... interfere in internal affairs under the guise of human rights.
"We once again urge relevant parties to stop making irresponsible remarks."
Speaking in Wellington, Kiwi Foreign Minister Nanaia Mahuta insisted the trans-Tasman statement was consistent with previous communiques.
"China has reacted in a very predictable way on the issues we've already raised with China," she said.
New Zealand and Australia have called on China to allow the United Nations to visit Xinjiang to conduct a "meaningful and unfettered" investigation.