The claim that it would cost the British economy £1 trillion to reach net zero carbon by 2050 is a "piece of propaganda of very little value", the UK's first climate chief has said.

Adair Turner warned that the figure, cited by former chancellor Philip Hammond last year to warn against the policy, was "very much not helpful for understanding" the reality of the situation.

The comments by Lord Turner, the economist who chaired the government's Committee on Climate Change (CCC), come ahead of Wednesday's budget in which it is hoped that the chancellor will announce new policies to fight climate change.

He said that in reality there was evidence the cost to the British economy could be zero, and that even if the assumptions the £1 trillion figure was based on were true it was still highly misleading.

"I very strongly believe that expressing the figure as £1tn or £1.3tn is very much not helpful for understanding of the figures for the following reason," Lord Turner told the Commons treasury committee.

"The way to help people think about ‘is there a cost of climate change mitigation and what is it’ is ... to say how much lower might your standard of living in 2050 be than it would otherwise be.

"That is what the CCC has said is in a range of 1-2 per cent in a worst case basis ... if you then put it through a model that says yes, but the very process of doing that would create incentives for new technological development that wouldn’t occur we know as a piece of economic theory that the cost would be less."

He continued: "But let’s suppose that it was 1.5 per cent. ... by setting these figures up you’re making people think ‘I’ve got to find a trillion’ to pay for that. These are tiny little slices at the end of 2050 people might have to accept being 1.5 per cent worse off than they otherwise would be.

"Which, if we're growing our economy at 1.75 per cent per annum, means they would reach in December 2050 that living standard that they would otherwise have reached in February 2050. That is a way, I think, that we can understand these figures.

"To be blunt, although I respect Philip in many ways, I think that letter was a piece of propaganda of little value in terms of its contribution to public understanding."

The hoped-for focus on climate change in the budget comes as UN experts warn the world is "way off track" for meeting targets to curb rising temperatures as the signs of climate change increase.

A report compiled by the UN's World Meteorological Organisation (WMO) highlights 2019's increasing heat, accelerating sea level rises, and extreme weather - and the impact they have on people and wildlife.

Philip Hammond, former chancellor, used the £1 trillion figure (AFP via Getty Images)

Last year was the second hottest year on record for the world, with a global average temperature of 1.1C above pre-industrial levels, the WMO's statement on the state of the global climate in 2019 confirms.

Later in the autumn the UK is hosting the COP26 conference in Glasgow where leaders are hoping to make progress on agreeing what contribution to cutting carbon emissions each country should make.

Giving advice on what individuals themselves could do themselves to address their carbon impact, Lord Turner added: "I think the issue of persuading people to eat significantly less red meat in particular is one that we're not going to be able to shy away from if we're serious about a zero carbon economy."

The peer appeared to upset Tory MP Harriet Baldwin, who said: "I'm increasingly worried that people as influential as yourself, Lord Turner, make these statements about red meat when you think about the difference between sustainably grown cattle and, you know, flying in soya beans from Brazil."

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. 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But Lord Turner replied: "The fact is they all produce methane emissions and methane is a very powerful greenhouse gas.

"We can't get around that. It doesn't mean people have to give up red meat, but I think the way forward is smaller consumption of red meat, but when you consume red meat have high quality, organic, low environmental impact."

Contrary to the MP's claim, soya beans do not tend to be transported by air as their delivery is not particularly time-sensitive, and surface transport in fact constitutes a relatively small proportion of the carbon emissions of all food.