The Green Party are hypocrites given their MPs' spending on flights, Act leader David Seymour says.
However, the Greens have dismissed the criticism as a "boring gimmick", and say it is caucus policy to offset all air miles.
Mr Seymour said the latest release of expenses shows that in October, November and December the average Green MP spent $7992 on air travel -- the highest average amongst political parties.
"Green MPs' expenditure on air travel is extraordinary for several reasons," said Mr Seymour. "These are the MPs who regularly tell us that climate change is the crisis of our time and we must reduce our emissions."
Mr Seymour said the average Green spend of $7992 compared with an average spend by Labour MPs of $7790, $5493 by National MPs, and $5998 by NZ First MPs.
A Green Party spokesman dismissed Mr Seymour's attack as a "gimmick".
"Attacking our MPs' use of air travel is a boring, standard line that the extreme right resort to nearly every year.
"Air travel is a reality for MPs who work hard, especially for those who don't live in Wellington. It's also caucus policy to offset all our air miles."
The figures exclude ministers, who are generally required to travel more often. Mr Seymour spent $7422 on air travel -- only marginally lower than the Green Party average.
His office pointed to higher spending by leaders of parties. Green co-leader James Shaw spent $14,425.
Mr Seymour referenced the Greens' spending on flights during his keynote address to his party's annual conference in Orakei.
A self-described "climate luke-warmer", he argued Act's ideology was the best bet for protecting the environment, and announced policy to sell state-owned farmer Landcorp and put the proceeds in a trust that would give grants to groups running native wildlife sanctuaries.