The National Opposition has backed a joint call by the New Zealand and Australian Governments for China to allow unfettered access to Xinjiang province by the United Nations to investigate the treatment of Uighurs.
Former foreign minister Gerry Brownlee said he had spoken about it to China's ambassador to New Zealand, Wu Xi, and had been told China would facilitate access as soon as Covid-19 and terrorist threats had subsided.
But Brownlee said: "Now is the time to welcome these observers."
China had said human rights abuses against the Uighurs were lies and accused New Zealand and Australia of engaging in smear tactics.
"China can clear all this up by opening up to a UN investigative group."
The joint statement on Tuesday, issued by Foreign Minister Nanaia Mahuta and her Australian counterpart, Marise Payne, was part of a global initiative to pressure China over its treatment and detention of Uighurs.
They said they reiterated their "grave concerns about the growing number of credible reports of severe human rights abuses against ethnic Uighurs and other Muslim minorities in Xinjiang.
"In particular there is clear evidence of severe human rights abuses that include restrictions on freedom of religion, mass surveillance, large-scale extra-judicial detentions, as well as forced labour and forced birth control, including sterilisation."
They also welcomed sanctions that had been placed on some Chinese officials by Canada, the European Union, Britain and the United States.
"We underscore the importance of transparency and accountability, and reiterate our call on China to grant meaningful and unfettered access to Xinjiang for United Nations experts and other independent observers.
The Chinese Embassy issued a response, saying some countries had been "fabricating and spreading groundless disinformation about Xinjiang to smear China's image" and it was interference in China's internal affairs.
"Xinjiang-related issues are in essence about countering terrorism and deradicalisation, not about human rights," the statement said.
"We welcome all who really want to know Xinjiang's development to visit the region but we firmly oppose any condescending presumption of guilt."
Brownlee's statement marks a shift for National. National has been less gung-ho about criticising China than the Coalition government under Foreign Minister Winston Peters, or Mahuta under the Labour Government.
Brownlee has also voiced caution over New Zealand issuing joint statements with more strident members of the Five Eyes intelligence alliance, as has been done in criticisms of China's clampdown on democracy in Hong Kong.
New Zealand had always had a good dialogue with the Chinese Government, Brownlee told the Herald this year.
"It seems to me we should be continuing with that policy where we are talking about those issues rather than lining up with others who are a little more strident and, if I can also say, a lot less dependent on China than New Zealand is."
It now appears that as an alternative to signing up to Five Eyes statements, which are likely to inflame China, New Zealand will mix it up more, such as joint statements with just Australia.
The statement on the Uighurs is the second joint statement in two weeks between New Zealand and Australia – the other one was on changes to electoral law by China's National People's Congress that eroded democracy in Hong Kong.