The Australian Youth Climate Coalition joined crossbench politicians on the lawns in front of Parliament House on Wednesday, while Extinction Rebellion looked to push through their message with protest trucks.

"The rest of the world is looking at how to use stimulus through green recovery and this government's wasted that opportunity," Greens Senator Sarah Hanson-Young said at the post-budget event.

"The environment's the big loser."

Alex Fuller from the AYCC said young people had been shunned by Treasurer Josh Frydenberg.

"Why is the Morrison government giving money hand over fist to fossil fuel corporations when so many families are doing it tough?"

Independent MP Zali Steggall said there should have been bonuses for resilience and climate adaptation in homes, as well as support for people tackling coastal erosion.

"By investing in their short-term political survival, and nothing else, they should be held to account," Ms Steggall said.

"In this place, we are making decisions that impact on your life, your future, your livelihood."

The Greens said the government was handing $1.1 billion in new money to the oil, gas and coal industry - with $11.4 billion in the next year alone - adding to a total of $51 billion across four years.

The federal budget locked in $1 billion for measures to lower emissions and $58.6 million to support an expansion of the gas industry.

Mr Frydenberg said in his budget address Australia was "playing its part on climate change" and was on a path to net zero emissions.

"Our goal is to get there as soon as we possibly can, preferably by 2050."

Australian Associated Press