New York - Microsoft co-founder Bill Gates regained the top spot on Forbes' annual list of the world's richest people released on Wednesday as investment guru Warren Buffett and Mexican telecom magnate Carlos Slim each lost 25 billion dollars.

Gates lost just 18 billion in the financial apocalypse that hit world markets last year and is now worth 40 billion dollars compared to Buffet's 37 billion dollars and Slim's 35 billion dollars.

The financial devastation took a heavy toll on the world's billionaire's club, with the top 10 richest people losing a total of 238 billion dollars - more than the gross domestic product of Ireland or Israel.

In total the number of billionaires in the 2009 rich list fell to 793 from 1,125 a year earlier, while the total net worth of the billionaire's club was just 2.4 trillion dollars - down from 4.4 trillion dollars the year earlier.

The average billionaire is now worth 3 billion dollars, down from 3.9 billion dollars in 2007.

The year's biggest loser was India's Anil Ambani, who saw his value decline by 31.9 billion dollars to 10.1 billion dollars. His compatriot Lakshmi Mittal also suffered staggering losses. His fortune plummeted 25.7 billion dollars to 19.3 billion dollars.

Billionaires whose fortune increased were few and far between. One was New York Mayor Michael Bloomberg who bought back a 4.5 billion dollar chunk of his financial services market from cash-strapped Merrill Lynch, while another was financial guru John Paulson, who made billions of dollars betting against the housing market.

The decline in fortunes hit especially hard in Russia and Asia, allowing Americans once again to dominate the rich list with 10 of the top 20 spots. New York replaced Moscow as the top billionaire city with 55 members of the rich list, followed by London with 28 billionaires and Moscow with 27.