National leader Bill English sits down with John Campbell for the first of Checkpoint's leader interviews in the lead-up to the election.
Watch the whole interview here:
In a wide-ranging interview, Mr English discussed the revelations about list MP Jian Yang, tax policy, the environment, the price of butter and the cost of living.
A story on the Newsroom website raised questions about the two-term MP's background in the Chinese military and intelligence. Dr Yang has since confirmed he taught spies, but denied he himself was a spy.
Mr English said Dr Yang was someone who had been open about his background in China.
"I am advised that he was clear about his CV when he was approved as someone suitable to be a candidate."
He said he could not recall when exactly he was told about Dr Yang's background. But he said Dr Yang functioned appropriately as a list MP and there was no question about his loyalty to New Zealand.
He declined to comment when asked whether or not he was briefed by the Security Intelligence Service.
"It's interesting it's surfaced 10 days out. It's been well known for five or six years.
"It's something that he was clear about."
On Labour tax policies, and National's approach to tax in the past, he said Labour's election campaign policies would mean the party would have to legislate for new rates of income tax.
Regarding Labour's proposed water tax - a plan to charge farmers one or two cents for every 1000 litres of water - he said National was already tackling environmental questions with the introduction of national water quality monitoring standards.
"We got on with the job.
"There was no agreed science on measuring water quality ... it is now settled and now we can measure progress.
''A water tax is just a dumb idea if you're trying to achieve environmental outcomes.
"The core argument here is that the tax is an indiscriminate way of raising revenue ... that is not the instrument that you use. The water tax is a blunt indiscriminate instrument."