A car crash television interview during which a Fox News host asked the author of a new biography about Jesus, why he, as a Muslim, feels able to write about the Christian Messiah, has had an unexpectedly positive outcome - with sales of the author's book increasing by 35 per cent in just two days.

The excruciating 10-minute interview, during which broadcaster Lauren Green was left with egg on her face after she tried to pin down respected scholar Reza Aslan, who just happens to be Muslim, on why he felt capable of writing a book about the life of Jesus, went viral at the weekend after it was posted on Buzzfeed.

Ms Green asks: “You’re a Muslim, so why did you write a book about the founder of Christianity?”

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To which a visibly surprised Mr Aslan responds: “I am a scholar of religions with four degrees, including one in the New Testament, and fluency in biblical Greek, who has been studying the origins of Christianity for two decades, who also just happens to be a Muslim.”

"It's not that I'm just some Muslim writing about Jesus," he continued. "I am an expert with a PhD in the history of religions."

But all publicity is good publicity, as they say, and this embarrassing episode for Fox News has had an extremely positive outcome for Mr Aslan whose controversial biography of Jesus, Zealot: The Life and Times of Jesus of Nazareth, has now reached number 1 in the Amazon books charts.

Publishers Random House had to rush to meet a surge in demand for the book, ordering an additional 50,000 copies to be printed on Monday, bringing the total copies in print to 150,000.

The biography, published on 16 July, had already been selling well prior to Mr Aslan’s appearance on Fox News, having reached number 8 in the Amazon book charts on Friday, but Mr Aslan is “thrilled” at the increased exposure on the back of the viral interview.

“I’ll be perfectly honest — I’m thrilled at the response that people have had to the interview,” Mr Aslan told the New York Times. “You can’t buy this kind of publicity.”

The Fox News interview has been watched nearly 4.5 million times on Buzzfeed, which posted the video under the title "Is this the most embarrassing interview Fox News has ever done?", and Mr Aslan has gained an additional 5,000 Twitter followers since it went out.

The book is to be published in the UK by The Westbourne Press with the ebook available from today and the hardback in bookstores from 15 August.