Mitchell said the Government of the Hong Kong Special Administrative Region was paying for his trip after reaching out to him in July last year with an invitation. The week-long trip was billed as promoting inter-parliamentary relations, he said.
"I'm very interested in their justice system," Mitchell said.
"I'll be at police college, a corrections facility, and have meetings with several high-ranked justice officials. I'll be interested holistically to see how the whole system works and how efficient it is, but also in what sort of programmes they run for rehabilitation."
Mitchell said he did not plan to raise any questions about New Zealand-China relations in Hong Kong, but described his trip as an auspicious invitation at a time when relations were strained.
Following claims — rubbished by the Government — that Cabinet ministers were awaiting permission to gain entry to China, Mitchell joked that he could try to sneak some in with him.
It was important for National to show countries, including China, how it valued their relations, he said.
"We will continue to manage that with countries important to us, because we have to show we are responsible and ready to move back into a governing role again."
A spokesman for Ardern said National's claims that ministers had been denied visas to enter China were wrong.
"Any assertion Mr Mitchell is getting some kind of preferential access is incorrect as there are currently no ministers waiting for permission to enter. The relationship with China is across many fronts and continues as per normal, and it is a good thing that those relations with the Opposition continue as well."
She has attributed the postponement of her trip to scheduling issues.
Foreign Minister Winston Peters called the trip a "marvellous idea".
"It'll certainly help with Mark Mitchell's education," he quipped.
Tourism Minister Kelvin Davis said the postponement of the China-NZ Year of Tourism launch was simply a scheduling issue, and he rubbished reports about a Chinese traveller cancelling plans to come to New Zealand because of the Government Communications Security Bureau's decision in November to block Spark from using Huawei to build the national 5G network for security reasons.
"One Chinese person out of a billion does not constitute a trend," Davis said.
Agriculture Minister Damien O'Connor said he had a chat with former National Party Prime Minister Dame Jenny Shipley, who chairs Oravida, at Waitangi this month. "It's clear National is trying to stir things up for political means when it's business as usual on the trading front."
Shipley told the Weekend Herald she had told O'Connor "a company I'm associated with was facing challenges in China and in a brief conversation explained the details of what we were experiencing".
"He replied that he would raise it with [the Ministry for Primary Industries] and I thanked him for that. I believed that the Minister would view this change we as exporters were experiencing as a matter of importance that any Government would wish to be aware of."
National's trade spokesman Todd McClay said O'Connor needed to stop "playing politics" and urgently repair NZ-China relations.
MPI director of market access Tim Knox said yesterday it was business as usual for New Zealand exports to China.
"As with any large trading relationship, temporary technical trade issues can occur from time to time with products at the border."
While Sanford did not attribute the issues to NZ-China relations, chief customer officer Andre Gargiulo said no reason had been given.
Government sources said Sanford, which has National Party president Peter Goodfellow on its board, was trying to score political points, and one complainant about export delays was Shipley.
Goodfellow, through a spokesman, "categorically denied" playing any role in public comments from Sanford about export delays.
McClay said there were "clear signs of a deteriorating relationship with China, caused by this Government and causing issues for exporters".
