Saudi Arabia's Kingdom Holding chairman Prince Alwaleed bin Talal  has disputed the Forbes 2013 billionaire listing, claiming that it understated his wealth, a report said. The Forbes list ranked the Saudi billionaire 26th on its list released on Monday, saying he had a wealth of $20 billion.  Mexico's Carlos Slim remained the richest person in the world with a fortune of $73 billion and Microsoft co-founder Bill Gates held on to the No. 2 spot with a net worth of $67 billion, according to Forbes' 2013 annual ranking of billionaires. Spain's Amancio Ortega, the co-founder of the Inditex fashion group, leapt over Warren Buffett and France's Bernard Arnault to become the world's third richest person on the list, with an estimated net worth of $57 billion. However, Prince Alwaleed accused Forbes of a "flawed" valuation method that undervalued his assets and "seemed designed to disadvantage Middle Eastern investors and institutions", said a report in The Guardian website. Prince Alwaleed  estimates his wealth at $29.6 billion, which would put him among the top 10 of the richest people, said the report. It said the prince had written to Forbes' editor-in-chief Steve Forbes, saying he will no longer provide the magazine with information about his finances and has reportedly instructed lawyers over the matter. Alwaleed also said he would continue to work with the Bloomberg Billionaires index, which was launched last year as a rival to Forbes' long-established list. Bloomberg estimates the prince's wealth at $28 billion, ranking him the world's 16th wealthiest person, the report said.Meanwhile, the US led the Forbes list with 442 billionaires, followed by 386 from Asia and the Pacific region, with 122 in China alone. Europe was close behind with 366, including 110 in Russia. The Americas, not including the United States, had 129 and the Middle East and Africa 103. Prince Alwaleed ranks 26th on the global list. Saudi Arabian businessman Mohammed Al Almoudi, who is ranked 65th on the list, has a wealth of $13.5 billion, according to Forbes. Ortega's fortune increased $19.5 billion, the biggest gain for any of the billionaires, from the report in 2012. He jumped two places and bumped Buffett, chairman and chief executive of conglomerate Berkshire Hathaway Inc with a fortune of $53.5 billion, out of the top three to the No. 4 spot for the first time since 2000. "Warren had a great year, it's just that Amancio Ortega had a better year," Forbes magazine editor Randall Lane said of the co-founder of Zara. "He has one of the dominant apparel lines in Europe." Arnault, of the LVMH luxury goods group, dropped to 10th place with $29 billion. Slim, 73, made much of his fortune in telecommunications but also branched out into retail, commodities, finance and energy. "To see Carlos Slim again broaden his lead and certify himself as the richest man in the world is a statement that wealth truly is global and not an American monopoly like it sometimes felt for many decades," Lane added in an interview. Rising stock markets fueled in part by monetary stimulus by the U.S. Federal Reserve, and robust consumer brands fortified the fortunes of those already on the list and drove many of the 210 new billionaires onto it. Oracle Corp's Larry Ellison, with a fortune of $43 billion, rounded out the top five in the ranking that included a record 1,426 billionaires, with an average net worth of $3.8 billion. Forbes' 27th annual ranking  is the biggest ever and has the largest jump in total number of people added in one year. "It is a very good year to be a billionaire, and a much easier year to be a billionaire. You have those economic forces and global markets going up and that is pushing more people over the threshold," Lane explained. Brazilian mining, energy and shipping magnate Eike Batista, whose net worth fell $19.4 billion, was the biggest loser on the 2013 list. He dropped from No. 7 in 2012 to 100. The total net worth of the world's billionaires is $5.4 trillion, according to Forbes, up from $4.6 trillion in the previous ranking. AMERICA, CHINA, RUSSIA HAVE MOST "There will be more Asian billionaires than American billionaires by the end of this decade, actually by the middle of this decade," said Lane. "That is a statement about where global growth is." Americans captured five of the top 10 spots including brothers Charles and David Koch, owners of Koch Industries Inc, who tied for sixth place with $34 billion each. France's Liliane Bettencourt, of the L'Oreal cosmetics empire, is the world's richest woman, coming in ninth with a $30 billion fortune. Li Ka-shing, who controls the Hong Kong-based conglomerate Hutchison Whampoa, is the wealthiest man in Asia with a $31 billion fortune, putting him in eighth place. New York Mayor Michael Bloomberg, the founder of financial data firm Bloomberg LP, a competitor of Thomson Reuters Corp , just missed the top 10, rising to 13th place from 20th with a net worth of $27 billion. WOMEN MAKE GREATER STRIDES Thirty-four more women, including American fashion designer Tory Burch, made the list for a total of 138. The youngest billionaire was 28-year-old Internet entrepreneur Dustin Moskovitz. The former college roommate of Facebook founder Mark Zuckerberg and an early investor in the social networking site, came in at No. 353 with a net worth of $3.8 billion. Another newcomer was GoPro's Nicholas Woodman with a fortune of $1.3 billion. The privately owned company makes wearable cameras. Renzo Rosso of the Italian fashion company Diesel was also new to the list with a $3 billion net worth. "It's a cultural sea change when you can come up with an idea, actualize the idea, monetize the idea and become a billionaire by your 40th birthday. That just didn't happen in the pre-Microsoft era," Lane said of the young billionaires. US banker and philanthropist David Rockefeller, 97, was the oldest, placing 527th with $2.7 billion. Sixty people dropped off the list, including Mark Pincus of social gaming company Zynga and Aubrey McClendon, the outgoing CEO and former chairman of natural gas producer Chesapeake Energy Corp.