Prime Minister Jacinda Ardern has pushed back on claims out of Australia that intelligence assessments pointed the finger at China's spy agency as being behind the burglaries of Anne-Marie Brady.

A year-long New Zealand police investigation into the affair, looking into three burglaries of the home and office of the University of Canterbury professor, was closed in February with the case officially described as "unresolved".

But last night Australia's Four Corners current affairs TV show said conclusions had been reached behind closed doors in Canberra.

"Government sources have confirmed to Four Corners that intelligence assessments identified China's spy service as