SIR David Attenborough has warned that climate change will bring “great social unrest” within decades.

The naturalist has already predicted grave consequences for humans if global heating cannot be slowed down.

Now he has turned his ire directly at climate sceptics in power, especially in America and Australia.

Giving evidence to the House of Commons Business, Energy and Industrial Strategy Committee yesterday, Sir David said he was “sorry that there are people in power internationally” who failed to champion efforts to reduce emissions of greenhouse gases.

Sir David did not name President Donald Trump but he stressed such leaders were “notably” to be found the United States, “but also in Australia, which is extraordinary actually because Australia is already having to deal with some of the most extreme manifestations of climate change”.

The 93-year-old broadcaster has already predicted grave consequences for humans if global heating cannot be slowed down.

However, Sir David, increasingly one of the most important voices fighting global heating, did not strike a pessimistic tone. Public opinion, he suggested, was turning in the way it did against slavery in the 19th century.

He told MPs: “The most encouraging thing that I see, of course, is that the electors of tomorrow are already making themselves and their voices very, very clear.

“And that is a source of great comfort in a way, but also the justification, the reality, that these young people are recognising that their world is the future.

“I’m OK, and all of us here are OK, because we don’t face the problems that are coming. But the problems in the next 30 years are really major problems that are going to cause social unrest, and great changes in the way that we live, and what we eat. It’s going to happen.

“There was a time in the 19th century when it was perfectly acceptable for civilised human beings to think that it was morally acceptable to actually own another human being for a slave. And somehow or other, in the space of 20 or 30 years, the public perception of that totally transformed.”

He added: “I suspect that we are right now in the beginning of a big change. Young people in particular are the stimulus that’s bringing it about.

“People are understanding that to chuck plastic into the ocean is an insult. To have the nerve to say: ‘This is our rubbish. We’ll give you money and you can spread it on your land instead of ours, in the far east,’ is intolerable. And for some reason or other young people understand that. And that’s a source of great hope to me.”

Sir David’s broadcasting - including the Blue Planet series he narrated - has been credited with turning around attitudes to pollution.

But he said he had not set out to be a campaigner.

“I’d been putting it in programmes for years, but nobody took much notice of it,” he said. “And in Blue Planet II it was a sequence that lasted two minutes maximum, I should say, and yet for some reason – if I knew what the reason was I’d be a richer man, I dare say – it rang a bell in the public consciousness. I’ve never seen anything like it.

“I’m not by nature a propagandist. I started making natural history programmes because I thought there was nothing I would prefer to see more than the beauty of the natural world. And I would love to just go on doing that. That’s what I enjoy.”

Sir David did risk a political point. Asked about the UK Government’s target to reach net zero carbon by 2050, he questioned whether such approaches work.

He said: “In a way I would think that is not the way of focusing on the problem. “We cannot be radical enough in dealing with the issues that face us at the moment. The question is: what is practically possible? How can we take the electorate with us in dealing with these things?”

Scotland has committed to an earlier target, 2045. Many environmentalists think this is too late too.

The UK Government’s own advisors have rounded on climate change efforts for amounting to a “ramshackle, Dad’s Army” approach

In its annual progress report to Parliament, the advisory Committee on Climate Change (CCC) said UK action to slash the greenhouse gas emissions driving climate change is lagging far behind what is needed,

The group said the Government had to show it was serious about tackling the problem in the next 12 to 18 months.

And it warned that action to prepare homes, businesses and the countryside in England for a hotter world is “less ambitious” than it was a decade ago.

The committee assessed 33 areas where the risks of climate change needed to be addressed, from flood resilience of properties to impacts on farmland and supply chains, and found there was no good progress in any of them.

The UK is not prepared for 2C of warming, the level at which countries have pledged to curb temperature rises, let alone a 4C rise which is possible if greenhouse gases are not cut globally, the committee warned.

Committee chairman Lord Deben said: “The whole thing is really run by the Government like a Dad’s Army.

“We can’t go on with this ramshackle system, which puts huge pressure on individuals, who are reacting well but the system is not fit for purpose, and doesn’t begin to face the issues.”

More action is needed to prevent overheating in homes, hospitals and schools as the risk of heatwaves rises, to tackle flash flooding from heavy downpours, cut water consumption and protect soils and wildlife habitats in England.

There has also been little progress on many areas for cutting emissions, and the gap between what is being done and what needs to be done to meet existing targets to curb climate change is growing, the committee warned.

The committee’s chief executive Chris Stark said a “’get real’ moment” had arrived for those parts of government which were failing to act. Climate change, the CCC, was already here.