At the launch event in London, the prime minister will say the ban on new petrol and diesel cars could 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.

The change in plans, which will be subject to a consultation, is being planned because experts warned the previous target of 2040 would still leave old conventional cars on the roads after the clean-up date of 2050.

Image source, Reuters

The UN summit, known as the 26th Conference of the Parties, will be held in Glasgow in November and see participating countries assess progress on tackling climate change.

It will be attended by countries that have ratified the United Nations Framework Convention on Climate Change (UNFCCC), a treaty which came into force in 1994.

Around 200 world leaders will seek to agree a new, long term deal on rising temperatures.

The COP meeting in Madrid last year saw a compromise deal struck on curbing carbon pledges but left a raft of complex issues unresolved.

BBC Radio 5 Live

Image source, EPA

Chancellor of the Duchy of Lancaster Michael Gove has responded to Claire O'Neill's comments.

"I love Claire, she’s a close friend of mine, this is one area where I disagree," he tells BBC Radio 5 Live.

He says Boris Johnson has described his political outlook as "that of a green Tory".

Mr Gove says the government wants to fight to ensure the planet is handed on to the next generation in a better state.

He confirms that the cabinet sub-committee on climate had not met yet - which was one of the criticisms from Ms O'Neill.

But he says other ministers have discussed the issue and the "very first item" on the cabinet agenda this year was the climate change conference.

Today Programme
BBC Radio 4

Image source, Getty Images

Claire O'Neill, who was sacked by Boris Johnson from her role as the head of this year's vital climate summit, has launched a scathing attack on the prime minister this morning.

Ms O'Neill told the BBC she had been the target of "dark ops, negative, defamatory briefings" by Downing Street.

She said Mr Johnson - who appointed her and offered her a post in cabinet - had shown "a huge lack of leadership and engagement".

She said he had told her he "didn't get climate change".

"My advice to whom Boris is making promises… is to get it in writing, get a lawyer to look at it and make sure the money is in the bank," she added.

The former Tory minister also suggested there was even a doubt over whether the conference - due to go ahead in Glasgow in November - would go ahead there or be moved to an English location.

Read more here

The prime minister is expected to outline environment policies including government plans to bring forward 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.

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.

Ahead of his speech, the prime minister said that hosting COP26 was “an important opportunity for the for the UK and nations across the globe to step up in the fight against climate change”.

This morning the prime minister is giving a speech to launch the next UN climate conference – called COP26.

Boris Johnson will be joined by Sir David Attenborough at the event in London’s Science Museum.