The Microsoft co-founder had topped the Forbes business magazine's rich-list for the past 13 years.

Mr Buffett's wealth increased by $10bn (�5bn) last year to $62bn.

Mr Gates's fortune climbed by $2bn during the same period, dragging him down to third on the list with a fortune of $58bn.

He was narrowly pipped into second place by the Mexican communications magnate Carlos Slim Helu, whose $60bn net worth has doubled in the past two years, Forbes reports.

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A record 1,125 individuals with a combined net worth of $4.4 trillion made it into Forbes' 2008 list of billionaires.

"The reason for this explosion in wealth is that we're in the midst of a phenomenal global boom," said Steve Forbes, chief executive of Forbes magazine.

"Never before in human history have so many people in so many parts of the world advanced so quickly economically as has happened in recent years."

Two-thirds of those on the list are classified as self-made billionaires, and 50 of them are under the age of 40.

Mark Zuckerberg, 23, the founder of the social networking site Facebook, joins the list as the world's youngest billionaire.

His $1.5bn fortune makes him the world's 785th richest person, Forbes reports.

Patrice Motsepe joins the list as South Africa's first black billionaire with a net worth of $2.4bn.

The world's richest woman is the French L'Oreal chief, Liliane Bettencourt, 17th on the Forbes list with a net wealth of $22.9bn.

Other inclusions in the ultra-rich list include US chat-show host Oprah Winfrey, ($2.5bn), property mogul Donald Trump ($3bn), and Harry Potter author JK Rowling ($1bn).

Biker to billionaire

Nicknamed the "sage of Omaha" because of his phenomenal investment success, Mr Buffett, 77, has stakes in a range of companies, including Coca-Cola, Procter & Gamble and Tesco.

Forbes says he filed his first tax return at the age of 13, claiming a $35 tax deduction for his bicycle.

After studying economics at New York's Columbia Business School under investment guru Benjamin Graham, he began purchasing shares in textile firm Berkshire Hathaway in 1962 before buying a controlling stake in 1965.

The company's stock price surged to a record $150,000 a share in December, just before Forbes formulated its 2008 ultra-rich list.

Two years ago, Mr Buffett pledged most of his Berkshire shares to the Bill & Melinda Gates Foundation.