Labour leader Chris Hipkins says if Luxon was being honest on his overseas trips he would be saying the government is taking New Zealand backwards on climate.
Hipkins has been visiting a homeless youth support organisation in Auckland, as well as the Auckland Central Budgeting service, before speaking to media on Wednesday.
He targeted the government's climate strategy, announced this morning.
"I think the government are an absolute disgrace when it comes to tackling climate change. They have wound back almost every measure we had in place that was actually bringing down New Zealand's greenhouse gas emissions."
He said the strategy released today could not really be called an announcement.
"It's just three pages of platitudes, there's no real action in there that's going to reduce emissions and actually if you look at all the concrete action they're taking they're going to increase our emissions.
"They have cut $3b out of the climate change budget this year. Almost every decision they have taken since becoming the government has actually increased our emissions, rather than reduced our emissions."
"I don't think Christopher Luxon's going around the world and saying 'Hey everybody, look at New Zealand, we're going backwards on climate change at the moment', but that's what he should be saying if he was being honest."
He said the public needed to see concrete action from the government on emissions reduction.
"If they're going to rely on the emissions trading scheme, they're going to have to do a much much better job of that than they have been. They also need to be upfront with New Zealanders about what that means: a higher carbon price through the emissions trading scheme means a higher price every time you fill up the car.
"It means higher cost of living, and it's not the most effective way of reducing our emissions."
He said the changes to the clean car standards would simply exacerbate the problem of vehicle emissions.
"We should be driving down our emissions from transport, this government seems intent to drive them up."
With Christopher Luxon overseas in Washington DC to attend a NATO summit, Hipkins said the prime minister should also be using his platform to express New Zealand's views on Gaza.
"To condemn the ongoing supply of weapons to Israel, to call for an immediate ceasefire, and to call for a lasting peace. That would be consistent with New Zealand's proud tradition of being independent on these matters.
"I think the war in Gaza is unjust, there is a huge humanitarian crisis there now as a result of it, it must stop, and I think New Zealand should show leadership."
Hipkins earlier today heard from budget managers following the news that a third of budgeting services nationwide are losing funding.
He then travelled to KickBack Youth Homelessness on K Rd to meet with the community and learn about the work the organisation does.
