Mexican telecom giant Carlos Slim has topped Forbes magazine's billionaire's list.

It is the first time since 1994 that an American has not led the rankings.

Mr Slim has beaten Bill Gates from the top position after estimates of his fortune rose by $18.5 billion from last year to $53.5 billion.

Microsoft founder Bill Gates is now in second place while US investor Warren Buffet has slid into third.

Bill Gates's fortune now totals $53 billion, while investment guru Warren Buffet is worth $43 billion.

The total number of billionaires on the 2009 list has risen from 793 to 1,0111.