A ban on sales of new petrol and diesel vehicles will be brought forward to 2035, under plans outlined as the Boris Johnson launches key UN climate talks in the UK.
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.
The Prime Minister said 2020 would be a "defining year of climate action" for 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 event on Tuesday, which was attended by Sir David Attenborough, will also kick off a year of climate action across the UK, the Government said.
The UN climate talks that were held in November were the most important since the Paris Agreement to curb global warming was secured in 2015.
Countries are expected to deliver more ambitious domestic plans for cutting greenhouse gases by 2030 – as current proposals are not enough to prevent dangerous temperature rises.
In a statement made ahead of the launch, Mr Johnson said the ban on selling new petrol and diesel cars would come even earlier than 2035, 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.