Prime Minister Rishi Sunak's recent policy changes could derail the UK's net-zero plans and threaten its position as a leader on climate change, an independent watchdog said.
He also lowered the proportion of households that will be required to replace their gas boilers with a low-carbon alternative. And he scrapped a plan to make landlords improve the energy efficiency of their properties.
The Commission on Climate Change, the government's own watchdog, said the policy shift would have a negative impact on household finances and would make it more difficult to reach the UK's stated target of zero emissions by 2050.
"We remain concerned about the likelihood of achieving the UK's future targets, especially the substantial policy gap to the UK's 2030 goal," said Piers Forster, a professor of climate physics and the commission's chair.
"Around a fifth of the required emissions reductions to 2030 are covered by plans that we assess as insufficient," he added.
"Recent policy announcements were not accompanied by estimates of their effect on future emissions, nor evidence to back the government's assurance that the UK's targets will still be met."
Mr Forster urged Mr Sunak's government to adopt "greater transparency in updating its analysis at the time of major announcements".
He also urged the government to "restate strong British leadership on climate change" in the period leading up to Cop28.
“Our position as a global leader on climate has come under renewed scrutiny following the Prime Minister’s speech", he said.
In its analysis of Mr Sunak's announcements, the commission warned that renters would have to pay more for energy in their less efficient houses. Drivers who move to electric cars later rather than sooner will face higher costs through their vehicle's lifetime, it added.
UK emissions are supposed to fall by 68 per cent compared with 1990 levels by the end of the decade.
The 2030 target is seen as a critical step towards becoming net-zero by 2050 and stopping global temperatures climbing by more than 1.5 degrees Celsius above pre-industrial levels.
The Commission welcomed announcements on a deal to electrify steel production at the Port Talbot plant in Wales and the Zero Emission Vehicle mandate specifying that only 20 per cent of vehicles produced between 2030 and 2035 will be able to burn petrol or diesel at all.
A government representative said it was confident of reaching the net zero target and that it was taking a fairer and more pragmatic approach to reaching the goal that would save households money.
"The UK remains a global leader on climate – cutting emissions faster than any other G7 country – so we are confident that we will meet our future carbon commitments," the representative said.