Dr Yang, elected in 2011, has consistently pushed for closer ties between New Zealand and China as well as for worldwide policies that echoed those of China's Communist Party, the Financial Times said.
A New Zealand lawmaker who was born in China said Wednesday he taught Chinese spies while working at that nation's elite military colleges but had never engaged in any intelligence activities himself and was loyal to his new nation.
A New Zealand government MP has admitted teaching English to Chinese spies when he was a lecturer at a language institute run by China's spy agency.
To have taught at the Air Force Engineering College, Yang would have nearly certainly been an officer in Chinese military intelligence and a member of the Communist Party, Newsroom reported.
A joint investigation by Newsroom and Hong Kong's Financial Times claims New Zealand's Security Intelligence Service has investigated the Chinese-born MP, including interviewing a person about him previous year.
The National Party also released a copy of his CV from 2012 which mentioned his time at the Air Force Engineering College and Luoyang PLA University of Foreign Languages.
He said questions about Mr Yang should be addressed to the New Zealand authorities and that China "upholds the principle of not interfering in others' internal affairs".
Yang challenged "those who are propagating these defamatory statements" to front up and prove them.
On Wednesday, Yang admitted he had spent time at both institutions but insisted there had been nothing untoward about his work.
"Members of the Chinese community in New Zealand would have been obliged to respond to any fundraising request from him as a few would have been aware of his background, and present links to their homeland".
"If you define those cadets, or students, as spies, yes, then I was teaching spies, " he said.
"I don't think so".
National list MP Jian Yang beside party leader Bill English with "Blue Dragons" supporters at a party policy launch. However, in a Chinese-language interview with the Financial Times, Yang reportedly asked repeatedly that information about his academic past in China be omitted from any article about him.
Dr Yang said he had not had any involvement with the Communist Party since leaving China in 1994.
"By the year of my birth, in 1962, China had wiped out private ownership ... a horrific starvation had just passed with the deaths of millions of people ... by 1978 the Chinese economy was on the verge of collapse". "We are all aware of China's enormous economic growth ..."
But PM Bill English did not confirm whether Mr Yang had been investigated.