Mr Sunak delayed a series of flagship environmental policies, warning voters would revolt against the cost of making the UK a net zero carbon emitter by 2050.
The Prime Minister drew criticism from within his own party when he delayed measures including a ban on new petrol car sales from 2030 to 2035.
Mr Trump has weighed in behind the Prime Minister, saying Mr Sunak had “very substantially rolled back the ridiculous ‘Climate Mandates’ that the United States is pushing on everyone”.
The former US president said on his social media platform: “I always knew Sunak was smart, that he wasn’t going to destroy and bankrupt his nation for fake climate alarmists that don’t have a clue.”
Mr Trump, who is running for the White House in 2024, criticised the Biden administration for “merrily” spending “trillions of dollars trying to do that which is not doable”.
He added: “Congratulations to Prime Minister Sunak for recognising this SCAM before it was too late!
“The Green New Hoax will take down the US, perhaps even sooner than our Open Border of Death. IT MUST BE STOPPED. MAGA!!!”
US goal of net zero emissions by 2050
The US has also set a goal of achieving a net zero emissions economy by no later than 2050.
Joe Biden’s administration admits it is an “ambitious” aim but claims the US is “on a clear path to achieve this goal” through the president’s flagship legislation.
The plan includes the Inflation Reduction Act, which puts $375 billion in spending over a decade towards fighting climate change.
While it is an historic sum, it represents a slimmed-down version of an ambitious plan to supercharge environmental policy that Mr Biden had initially proposed.
A key goal for Mr Biden’s administration is to make the country a global leader in electric vehicle production.
Mr Sunak said he remains committed to the UK becoming a net zero carbon emitter by 2050, but has amended high-profile policies intended to help deliver that goal citing the “unacceptable costs on hard-pressed” families.
Last week, he announced he was delaying a ban on new petrol car sales from 2030 to 2035, the same date chosen by the European Union.
He pushed back the ban on new oil boiler sales from 2026 to 2035, while increasing heat pump grants to £7,500.
Mr Sunak also promised not to introduce new taxes to discourage eating meat or flying, ruled out orders for drivers to car-share, and scrapped plans for households to use up to seven bins for recycling.
The new stance prompted immediate blowback from within the Conservative Party, with Boris Johnson among the most high-profile Tory critics.
But Mr Sunak warned that politicians needed to be more honest and “realistic” about the costs involved in realising the UK’s net zero ambitions.
Labour said it would reinstate the 2030 deadline for the new petrol car ban if it wins the next general election.
Meanwhile, Mr Trump appears bent on reversing Mr Biden’s climate legislation if he wins a second term in next November’s presidential election.
The Republican frontrunner pulled the US out of the Paris climate accords, a global agreement to limit temperature rise this century.
His plans for a second term reportedly include blocking the expansion of the electrical grid for wind and solar energy and hollowing out the Environmental Protection Agency.
Mr Trump also plans to block moves by states including California to regulate car pollution levels.
Other prominent Republican candidates have hinted they will take a sledgehammer to Mr Biden’s environmental policies, including Vivek Ramaswamy, who called the climate change agenda a “hoax”.