"This is a significant event in terms of mapping out the globe's plans around emissions reductions.
"New Zealand does need to be represented – I feel really strongly about that.
"If we're not at the table, there are decisions that are made there that affect us - so we do need to be at the table."
There were also concerns Shaw would use up a space in a managed isolation facility on his return, but Ardern said the Government had gone to great lengths to minimise its use of MIQ spaces.
"We've had 170,000 New Zealanders move through our managed isolation facilities since we've had them in place - do you know how many ministers were a part of that number?
"Just the one - Damien O'Connor - for trade talks."
It was vital for Kiwi farmers that New Zealand attended these talks, Ardern said.
"We also make people aware of the good work that's been done by our rural community on agricultural emissions."
"I think we need to continue to make the case and promote the approach that New Zealand is taking."
As for Shaw's presence being hypocritical, Ardern said that was an issue Mackay should raise with the organisers of the conference.
Listen below:
Meanwhile, Ardern said it was important for rural people to get vaccinated, even though she accepted it could be more difficult in isolated areas.
"We need to keep making sure we make it easier for everyone in New Zealand to get vaccinated."
Vaccination rates were slightly lower in rural areas, Ardern said.
"Covid is not just a city virus – so we've got to get everyone vaccinated."
Also in today's interview: Ardern talked about how New Zealand's bipartisan political approach to vaccination meant a lower rate of vaccine hesitancy than the US and why she refused an Official Information Act request for information on Groundswell. She also addressed New Zealand's supermarket duopoly.
