Author Yuval Noah Harari has said Brexit is a “distraction” and a “fantasy”, adding that British politicians should instead focus on the threat of global warming.

The Israeli historian and author of bestsellers Sapiens and Homo Deus described the timing of Brexit as “terrible” and said every minute the British government spends on negotiations is a minute wasted.

Speaking at the launch of his new book, 21 Lessons for the 21st Century, he said Brexit was not in itself a bad idea but it came a “terrible” time.

He said: “As a historian I can say that it is basically a distraction. I don’t think that inherently it is a bad idea. It’s an okay idea. It’s just the timing is terrible.

“If you look at the three big problems of our time, nuclear war, climate change and technological disruption, Brexit is not helping us at all to tackle those. It’s doing the opposite.

“If the EU breaks up into 28 different countries it’s going to much more difficult to negotiate agreements, to have a common front against the high tech giants and so forth.

“So in this sense, every minute the British and EU institutions are spending on negotiations is a minute they don’t spend on climate change. And they spend a lot of minutes on Brexit.”

Harari’s two previous books, Sapiens, which examined early human history, and Homo Deus, which speculated on a post-human future, became international bestsellers, selling 12 million copies combined. His latest effort focuses on today’s pressing questions.

He added: “(Brexit) is just a fantasy about being independent. There are no longer any independent countries in the world.

“It doesn’t matter what is written on some document. You can’t be independent. Ecologically there are no independent countries in the world. You can’t build a wall against climate change or rising oceans.”

The author, 42, who lectures on World History at the Hebrew University of Jerusalem, also labelled Donald Trump’s speech at the UN General Assembly on Tuesday, where the US President was laughed at by world leaders, as “disturbing”.

He said: “Two days ago we heard the President of the United States give a speech at the UN against globalism, basically against global cooperation, which I found very disturbing.

“You can’t build a wall against nuclear winter or global warming and you can’t regulate artificial intelligence or technology on a national basis.”

21 Lessons for the 21st Century is published by Jonathan Cape and is available in hardback now.