Emissions from coal and gas could grow by 1.7 billion tonnes by 2050 if their use is extended another 15 years, analysis from the federal government has found.
The government evaluated data from the 2024 Integrated System Plan by the Australian Energy Market Operator (AEMO), which provides a road map for Australia's energy transition for the national energy market.
If coal and gas were extended to 2040 and paved the way for the coalition's nuclear energy plan, the additional CO2-equivalent emissions created would be almost four times Australia's current output, the government said.
The output would be the equivalent of keeping all of Australia's cars on the road for another 40 years or having the nation's most polluting plant - Hazelwood in Victoria - run for 106 years.
Federal Energy Minister Chris Bowen said the government was working to lower energy prices and emissions after a decade of delays.
But the progress was "precarious", Mr Bowen said, and any future delays would impede the government's emission goals.
"The coalition needs to come clean about its plan to reduce emissions and meet Australia's energy needs," he said.
Federal Opposition Leader Peter Dutton and the coalition have pledged to build seven nuclear plants across five states on the sites of coal-fired power stations if they win government.
An election must be held by May 17, 2025.
Plans to build nuclear plants could cost up to $600 billion and the coalition has said nuclear reactors could be online by 2037.
Wayne Smith from the Smart Energy Council said extending coal and gas for future nuclear power would be a "carbon bomb" for Australia and its emissions.
"This is coal keeper on steroids," he told AAP.
"It's coal keeper and gas keeper.
"You increase coal and gas, you reduce solar and renewables; you increase pollution and you increase power bills.
"That's a really dangerous deal."
Mr Smith said nuclear and solar "don't play well together".
"They cancel each other out," he said.
But shadow treasurer Angus Taylor said the coalition was advocating a range of energy solutions, to ensure the reliability of the national power grid.
"We're seeing the technology changing, and we're seeing attitudes towards nuclear changing all around the world," he told Sky News on Sunday.
"We've come to a view over time that this can play a role. It's not the only role.
"We need more gas in our system in the coming years, but it can be part of the mix, and it should be part of the mix ... the trouble with Labor is it's a renewables only strategy."
