Boris Johnson is pledging an earlier ban on new petrol and diesel cars, as he hits back at claims that his attempts to lead the world in tackling climate change are mired in “chaos”.

In a long-awaited first speech on the climate emergency, the prime minister will call on other nations to match the UK’s landmark legal commitment to achieve ‘net zero’ carbon emissions by 2050.

“There can be no greater responsibility than protecting our planet, and no mission that a Global Britain is prouder to serve,” he will tell a London reception attended by David Attenborough.

However, the flagship announcement – to end sales of new polluting cars in 2035, rather than 2040 – will still fall short of the call by his independent climate advisers to act by 2030.

The government has faced growing criticism that it has failed to announce practical measures to achieve the net zero target, despite hailing it as a world-leading measure.

Mr Johnson barely mentioned the climate crisis during the election campaign – and a strategy for achieving net zero emissions will not emerge until the end of the year.

The speech on Tuesday is intended to launch the strategy for delivering success at the crucial ‘COP26’ summit in Glasgow in November, which the UK will host on behalf of the United Nations.

It is widely seen as the last realistic chance for countries to pledge the deep cuts in emissions to hold global heating to no more than 2C – and prevent catastrophic climate change.

But the strategy was plunged into confusion on Friday when the intended summit president – former energy minister Claire Perry O'Neill – was abruptly sacked by Dominic Cummings.

Climate change: Decade's defining issue in pictures Show all 20 1 /20 Climate change: Decade's defining issue in pictures Climate change: Decade's defining issue in pictures California In this decade, humans have become ever more aware of climate change. Calls for leaders to act echo around the globe as the signs of a changing climate become ever more difficult to ignore Getty Climate change: Decade's defining issue in pictures Athens, Greece Fierce wildfires have flared up in numerous countries. The damage being caused is unprecedented: 103 people were killed in wildfires last year in California, one of the places best prepared, best equipped to fight such blazes in the world AFP/Getty Climate change: Decade's defining issue in pictures Redding, California Entire towns have been razed. The towns of Redding and Paradise in California were all but eliminated in the 2018 season AP Climate change: Decade's defining issue in pictures Athens, Greece While wildfires in Greece (pictured), Australia, Indonesia and many other countries have wrought chaos to infrastructure, economies and cost lives AFP/Getty Climate change: Decade's defining issue in pictures Carlisle, England In Britain, flooding has become commonplace. Extreme downpours in Carlisle in the winter of 2015 saw the previous record flood level being eclipsed by two feet AFP/Getty Climate change: Decade's defining issue in pictures Hebden Bridge, England Hebden Bridge in West Yorkshire has flooded repeatedly in the past decade, with the worst coming on Christmas Day 2015. Toby Smith of Climate Visuals, an organisation focused on improving how climate change is depicted in the media, says: "Extreme weather and flooding, has and will become more frequent due to climate change. An increase in the severity and distribution of press images, reports and media coverage across the nation has localised the issue. It has raised our emotions, perception and personalised the effects and hazards of climate change." Getty Climate change: Decade's defining issue in pictures Somerset, England Out west in Somerset, floods in 2013 led to entire villages being cut off and isolated for weeks Getty Climate change: Decade's defining issue in pictures Dumfries, Scotland "In summer 2012, intense rain flooded over 8000 properties. In 2013, storms and coastal surges combined catastrophically with elevated sea levels whilst December 2015, was the wettest month ever recorded. Major flooding events continued through the decade with the UK government declaring flooding as one of the nation's major threats in 2017," says Mr Smith of Climate Visuals Getty Climate change: Decade's defining issue in pictures London, England Weather has been more extreme in Britain in recent years. The 'Beast from the East' which arrived in February 2018 brought extraordinarily cold temperatures and high snowfall. Central London (pictured), where the city bustle tends to mean that snow doesn't even settle, was covered in inches of snow for day PA Climate change: Decade's defining issue in pictures London, England Months after the cold snap, a heatwave struck Britain, rendering the normally plush green of England's parks in Summer a parched brown for weeks AFP/Getty Climate change: Decade's defining issue in pictures New South Wales, Australia Worsening droughts in many countries have been disastrous for crop yields and have threatened livestock. In Australia, where a brutal drought persisted for months last year, farmers have suffered from mental health problems because of the threat to their livelihood Reuters Climate change: Decade's defining issue in pictures Tonle Sap, Cambodia Even dedicated climate skeptic Jeremy Clarkson has come to recognise the threat of climate change after visiting the Tonle Sap lake system in Cambodia. Over a million people rely on the water of Tonle Sap for work and sustinence but, as Mr Clarkson witnessed, a drought has severley depleted the water level Carlo Frem/Amazon Climate change: Decade's defining issue in pictures Addis Ababa, Ethiopia In reaction to these harbingers of climate obliteration, some humans have taken measures to counter the impending disaster. Ethiopia recently planted a reported 350 million trees in a single day AFP/Getty Climate change: Decade's defining issue in pictures Morocco Morocco has undertaken the most ambitious solar power scheme in the world, recently completing a solar plant the size of San Francisco AFP/Getty Climate change: Decade's defining issue in pictures London, England Electric cars are taking off as a viable alternative to fossil fuel burning vehicles and major cities across the world are adding charging points to accomodate AFP/Getty Climate change: Decade's defining issue in pictures Purmerend, The Netherlands Cities around the world are embracing cycling too, as a clean (and healthy) mode of transport. The Netherlands continues to lead the way with bikes far outnumbering people Jeroen Much/Andras Schuh Climate change: Decade's defining issue in pictures Xiamen, China Cycling infrastructure is taking over cities the world over, in the hope of reducing society's dependency on polluting vehicles Ma Weiwei Climate change: Decade's defining issue in pictures Chennai, India Despite positive steps being taken, humans continue to have a wildly adverse effect on the climate. There have been numerous major oil spills this decade, the most notable being the BP oil spill in the Gulf of Mexico in 2010 AFP/Getty Climate change: Decade's defining issue in pictures Amazon rainforest, Brazil More recently, large swathes of the Amazon rainforest were set alight by people to clear land for agriculture AFP/Getty Climate change: Decade's defining issue in pictures California This decade may have seen horrors but it has led to an understanding that the next decade must see change if human life is to continue Getty

She will be replaced by a minister, in a reshuffle expected next week, but that in turn has prompted fears of a conflict with the desire to strike post-Brexit trade deals, downgrading carbon commitments.

In the Commons, Rachel Reeves, the newly-elected chair of the business, energy and industrial strategy committee, tore into the “chaos and confusion”.

“Hosting the global climate conference COP26 is a huge opportunity for Britain to tackle the climate emergency and play an international leadership role,” she said.

“The prime minister has failed to chair a single meeting of the climate Cabinet committee and now he has sacked the conference president. Why is that?”

At the reception, the transport secretary Grant Shapps will announce a consultation on ending sales of petrol and diesel cars, including hybrids, by 2035 or “earlier if a faster transition is feasible”.

He will claim the switch to electric cars “is working”, adding: “We want to go further than ever before. That’s why we are bringing forward our already ambitious target to end the sale of new petrol and diesel cars.”

Giuseppe Conte, the Italian prime minister, will attend the event, along with prominent British figures from climate science and business.