Queen Elizabeth II was dismayed that Lord Cameron left the fate of Britain's membership with the European Union to a public vote, former US President Barack Obama has revealed. The late Queen, who as monarch had to remain politically impartial and expressed no public views on Brexit, is said to have discussed the matter with the then US President over lunch.

Recalling the conversation in a new book about the Queen's relationship with America, Mr Obama said she did not believe that "as big a decision" as the UK leaving the European Union "should have been decided by plebiscite".

He said: "'She [Elizabeth II] said, effectively, 'It's hard to understand why a prime minister, who presumably understands politics, would put a public referendum forward that he didn't know what the answer would be of such importance'."

Mr Obama was interviewed by award-winning US journalist Susan Page for her new book, The Queen and Her Presidents: The Hidden Hand That Shaped History.

He is one of four presidents and three prime ministers to be interviewed for the book, with traces her relationship with 13 US Presidents - right up to Donald Trump.

In an account of a 2016 lunch with President Obama the author writes: "They discussed the biggest current controversy in Great Britain, over Brexit. Her view on whether to leave the European Union was the subject of endless speculation during her reign and after her death."

The Queen, who famously wore a blue hat with yellow flowers that bore a striking resemblance to the European Union flag, never discussed her views on the political matter - though there has been much speculation on the matter.

But Ms Page says that she openly discussed the topic with Mr Obama, with whom she enjoyed a warm relationship.

"At the fercest time of the furore, she had expressed her real views to Obama," she writes. "It was a sign of the affinity and the trust she felt for him. At their luncheon, she was not only wary of Brexit but also dismayed by how Cameron was handling it - a very rare royal critique of a prime minister, in public or private.

"In a calculation that turned out to be disastrously wrong, Cameron had called a referendum for June, two months away."

It was understood to be the only time she had remarked to him about contemporary British politics.