Sunak is expected to set out his plans in a speech later this week, promising a “proportionate” approach.
Measures being considered include weakening the plan to phase out gas boilers from 2035 and delaying the ban on the sale of new petrol and diesel cars – currently due in 2030 – by five years, the BBC reported.
Sunak stressed that the government remains committed to the target of net zero emissions by 2050, but will achieve it “in a better, more proportionate way”.
He said that politicians “of all stripes have not been honest about costs and trade offs” and accused previous Conservative governments of taking “the easy way out, saying we can have it all”.
Sunak, who is attempting to draw a dividing line with Labour before the next general election, sought to position himself as the bringer of “real change” who would “put the long-term interests of [Britain] before the short-term political needs of the moment”.

The prospect of a major shift in the Conservatives’ approach was swiftly condemned by the green wing of the party.
Former COP26 president Alok Sharma warned that watering down the commitments could cost the Tories votes.
He told BBC Radio 4’s “Today” programme: “I think it’d be incredibly damaging for business confidence, for inward investment, if the political consensus that we have forged in our country on the environment and climate action is fractured.
“And frankly, I really do not believe that it’s going to help any political party electorally which chooses to go down this path.”

Sharma said delays on policies such as banning new petrol and diesel cars could mean tougher curbs in other areas.
Former Conservative Cabinet minister Simon Clarke said that it was in the party’s “environmental, economic, moral and [yes] political interests” to lead on net zero “rather than disown it”.
Some Conservative MPs are considering writing letters of no confidence in the prime minister if he goes ahead with the changes, the PA news agency understands.
Chris Skidmore, a Conservative former energy minister who led a government-commissioned review on net zero, told PA: “Rishi Sunak still has time to think again and not make the greatest mistake of his premiership, condemning the UK to missing out on what can be the opportunity of the decade to deliver growth, jobs and future prosperity.”

Tory peer Zac Goldsmith, who quit as environment minister in June with a scathing attack on Sunak’s “apathy” on the green agenda, said: “His short stint as PM will be remembered as the moment the UK turned its back on the world and on future generations. A moment of shame.”
But Craig Mackinlay, leader of the Conservative Net Zero Scrutiny Group which has been sceptical of the government’s policies, said the expected announcements by Sunak were “sensible and pragmatic”.
“I hope to mark this down as a sensible win for consumers,” he said, claiming his group’s “research and representations” may have influenced the move.
Conservative Karl McCartney, a member of the Commons Transport Select Committee, said he had pushed the government to delay the ban on new petrol and diesel cars, bringing it in line with the European Union which has moved the date to 2035.
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“I am pleased the government has seen the light,” he said.
“The costs to normal drivers will be too high, the electric charging infrastructure will not be in place and the technology is too reliant on China.
“The only people who will complain about this delay are the central London eco-zealots who do not live in the real world and are rich enough not to be affected.”
The party’s success in the summer’s Uxbridge and South Ruislip by-election, won largely through a campaign against the expansion of the ultra low emission zone (ULEZ), has led to some Conservative MPs to call for Sunak to water down or abandon net zero pledges.
The prime minister could reportedly also axe plans for new energy-efficiency targets for private rented homes.
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Liberal Democrat climate and energy spokesperson Wera Hobhouse said the prime minister has “cowered to the delayers and deniers like the disgraced Liz Truss and adopted wholesale their policies”.
Labour’s shadow energy secretary Ed Miliband said: “This is a complete farce from a Tory government that literally does not know what they are doing day to day.”
Green Party MP Caroline Lucas said: “This decision would be economically illiterate, historically inaccurate and environmentally boneheaded.”
Friends of the Earth’s head of policy, Mike Childs, said: “Rolling back on key climate commitments as the world is being battered by extreme flooding and wildfires would be morally indefensible.”