The last date to buy a new petrol, diesel or hybrid car in the UK will be brought forward from 2040 to 2035 at the latest, under government plans.
The change comes after experts said 2040 would be too late if the UK wants to achieve its target of emitting virtually zero carbon by 2050.
Boris Johnson will outline the policy later at an event to launch a United Nations climate summit in November.
He will say the summit is a chance to “step up” protecting the planet.
The summit, known as COP26, is being hosted in Glasgow. It is an annual UN-led gathering set up to assess progress on tackling climate change.
The government’s plans come as COP26’s former president Claire O’Neill, who was recently sacked, wrote a bitter letter accusing Mr Johnson of failing to support her work.
At a launch event in London the prime minister will say the ban could come even earlier than 2035 for new petrol and diesel cars, if possible.
Hybrid vehicles are also now being included in the proposals, which were originally announced in July 2017.
People will only be able to buy electric or hydrogen cars and vans, once the ban comes into effect.
The change in plans, which will be subject to a consultation, is being planned because experts warned the previous target date of 2040 would still leave old conventional cars on the roads after the clean-up date of 2050.
Mr Johnson is expected to say: “Hosting COP26 is an important opportunity for the UK and nations across the globe to step up in the fight against climate change.
“As we set out our plans to hit our ambitious 2050 net zero target across this year, so we shall urge others to join us in pledging net zero emissions.
“There can be no greater responsibility than protecting our planet, and no mission that a global Britain is prouder to serve.”
Sir David Attenborough will attend the launch.
Friends of the Earth’s Mike Childs said the government was “right” to bring forward the ban, but that 2030 would be better than 2035.
“A new 2035 target will still leave the UK in the slow-lane of the electric car revolution and meantime allow more greenhouse gases to spew into the atmosphere,” he said.
He said the government could show “real leadership” ahead of COP26 by reversing plans to develop “climate-wrecking roads and runways”.
AA president Edmund King said: “Drivers support measures to clean up air quality and reduce CO2 emissions but these stretched targets are incredibly challenging.”
The announcement comes as Ms O’Neill said she may sue the government after being sacked as COP26 president last week..
In her letter, she accuses Mr Johnson of promising money and people to support her work, but failing to deliver either.
The former Conservative energy minister said: “The cabinet sub-committee on climate that you promised to chair, and which I was to attend, has not met once.
“In the absence of your promised leadership… departments have fought internal Whitehall battles over who is responsible and accountable for (the conference).”
Downing Street has not yet replied to her accusations.
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