Churchill would never have voted UKIP - Boris

Mr Johnson, who has backed a referendum and said Britain must make clear it is ready to leave the EU if it does not get the reforms it wants, insisted that the wartime Prime Minister would not have been “a Ukip man” if he were alive today.

Speaking to the Radio Times about his new book The Churchill Factor, Mr Johnson said he was “genuinely obsessed” by the former PM, and used his example as a “justification” for his own approach to politics - including his prolific journalism and his liquid lunches.

But he denied that he was seeking to use his volume - which notes Churchillian traits including “the journalism, the love of show, the rhetorical flourishes, the sense of history ... the slight air of camp and the inveterate opportunism” - to draw comparisons between himself and his political hero.

Asked whether the book amounted to a covert leadership manifesto, he said: “No. No, I absolutely swear it isn’t.”

Mr Johnson, whose decision to stand in next May’s general election as Conservative candidate for Uxbridge and South Ruislip has been widely viewed as preparation for an eventual leadership bid, said that he had “changed as a politician” since becoming Mayor in 2008.

“The experience of running London for six or seven years has shown me what you have to do to get things done, and the energy and the application you have to put into it,” he said.

He hailed Churchill’s remarkable work-rate, combining high political office, authorship and journalism with a regular intake of alcohol through the day and into the night.

“I mean, what was he on? How did he do it?” said Mr Johnson. “He was incredible ... I mean, I can drink an awful lot at lunch and then write very fluently and fast, but if I drink at dinner, it just peters off.”

Asked whether, like Churchill, he used relentless activity to beat back depression, Mr Johnson said he put his own workaholism down to “the infantile desire for praise and approbation, probably. Something in our first four or five years conditions us.”

Considering what Churchill would have thought of the modern Conservative Party, the Mayor said: “I think he would have been a Tory, by today’s standards. I don’t think he would have been a Ukip man because he had a more generous conception of what it should all be about.

“If you read his European stuff, he’s pretty much all over the place but there is a consistency - he wants Britain to be involved. He would have wanted a renegotiation and I dare say a referendum too. All these, of course, are pretty idle speculations.”