The group believes if the coalition party room gives its members a conscience vote on the issue, a motion declaring the emergency can pass parliament.
"MPs and senators should have a conscience vote on the emergency declaration so that individual members of parliament can be held personally accountable by their constituents, their children and their grandchildren, indeed by all future generations, for the stance they took on the greatest economic, social, political and moral challenge of this century," Dr Hewson said.
Nearly three million Australians are living in areas where their local councils have declared climate emergencies and pledged greater action to combat climate change, including aiming for 100 per cent renewable energy and zero net emissions.
Countries including Britain, France and Canada have also made the call.
Greens MP Adam Bandt, who is leading the push in federal parliament, says the circumstances of record drought and fearsome bushfires at the start of spring underscore how severe the issue is.
"If the government can declare a budget emergency, it can declare a climate emergency," he said.
Independent Zali Steggall, who won former prime minister Tony Abbott's seat on a platform of strong climate action, cites the lessons of her business background in saying a problem has to be recognised and a plan formed before anything can change.
On Tuesday, she launched the latest Climate of the Nations report, which showed an overwhelming majority of people are concerned about the impacts of climate change and want stronger national action.
"People of all political leanings are concerned with this issue," she told reporters.
"It's something that I want to see more MPs stand up from both sides of the aisle and ask for a conscience vote.
"It should be a question for all MPs to represent their electorate and be true to the campaigns they run when they say they're going to take action on climate change."