Dozens of environmental groups have warned the prime minister they will not “stand by” while politicians use the environment as a “political football”.
More than 50 organisations have written to Rishi Sunak expressing “deep alarm” at reports his government may water down its green commitments.
They have requested an urgent meeting with the prime minister.
Mr Sunak said he was committed to meeting the 2050 net zero target in a “pragmatic and proportionate way”.
Some Conservative MPs have been calling for a rethink of certain green policies.
The prime minister has faced calls from some Tories to scrap his government’s policy of banning the sale of new petrol and diesel vehicles from 2030.
But earlier this week, cabinet minister Michael Gove said the government remained committed to the ban, which was announced in 2020 by then-Prime Minister Boris Johnson.
There has also been debate over the expansion of London’s clean-air zone.
Mayor of London Sadiq Khan’s plans to extend the capital’s ultra-low emission zone (Ulez) have been blamed as sealing the Conservative’s narrow by-election victory in Uxbridge last week.
On Friday, the High Court rejected a legal challenge against the plans.
But Mr Sunak has called on Mr Khan to “think twice” about the expansion, while Labour leader Sir Keir Starmer urged him to reflect on it amid the ongoing cost-of-living pressures.
The 52 signatories to the letter, dated July 28, include Friends of the Earth, Greenpeace UK, the National Trust, RPSCA and RSPB. They say they represent 20 million people.
After referencing recent wildfires across the globe, and flash flooding in India, they write that the environment “remains a central concern for voters” and there is “no public mandate for a delay”.
The letter concludes: “We will not stand by whilst politicians use the environment as a political football.
“It is courage and leadership that we need now. In the past, we have mobilised many of our members collectively with extraordinary results, and our resolve to stand firm now against any and all attacks on this critical policy agenda remains absolute.”
On Friday, speaking after the Ulez court decision, Mr Sunak said “banning things and stopping people from doing things is not the right approach” to reaching net zero,
He said his government would strive to meet the target without “unnecessarily adding costs and burdens to families, particularly at a time like now when the cost of living is a challenge for people with inflation”.
