Premier Daniel Andrews is adamant the state will reach net zero by 2045 despite suggestions his government could fall short of another key emissions target.
Closing power stations would not be enough to reach the target to slash emissions by up to 80 per cent by 2035, Environment Victoria warned in a report on Tuesday.
Rather, if the rate of consumption kept up, gas burned in Victorian homes and small businesses would account for up to 37 per cent of the state's emissions by 2035 - representing more than triple the existing share.
By closing coal power stations, there would be an annual "emissions gap" of between 18 and 24 million tonnes of carbon pollution, the organisation said.
It said other sectors would have to "step up" to fill the gap, but Mr Andrews maintained the state would get to net zero by 2045.
Some of the report's "binary" and "dramatic" conclusions assumed visibility of all future government projects and initiatives, Mr Andrews said.
"That's a moment in time comment," he told reporters on Tuesday.
"No peak body can know the full extent of the government's agenda or ambition when it comes to something like reaching net zero by 2045."
He confirmed the government was considering a proposal to build a gas terminal at Corio Bay but its commitment to reaching net zero remained iron-clad.
"We'll get to net zero by 2045," Mr Andrews said.
Deputy Victorian Greens Leader Ellen Sandell said the proposal has been on the planning minister's desk for more than six months and must be rejected.
"It will be a climate bomb, a climate disaster," she said.
If gas consumption declined slightly, Victoria's homes and small businesses would still account for up to 28 per cent of the state's emissions by 2035, the Environment Victoria report said.
That was at least double the existing share.
"What this report makes clear is that gas is set to become Victoria's biggest source of emissions if we don't take urgent action," Environment Victoria chief executive Jono La Nauze said.
"The Andrews government has world-leading climate targets and a comprehensive plan to shift the electricity sector from coal to renewables, but more than two million homes are still hooked up to fossil gas, a highly polluting and increasingly expensive fuel.
"Continuing to burn gas at the current rate, as some LNG import terminals have proposed, would result in household gas being responsible for about one third of the state's total emissions in a dozen years."
Environment Victoria called on the government to update its gas distribution road map with clear timelines, more ambitious goals, and incentives to push households to switch to electric appliances.
Mr La Nauze said any program needed to be targeted at low-income households, renters and diverse communities.
"The Andrews government should reject LNG import terminal proposals that are based on high levels of gas consumption continuing for decades," he said.
