Mukesh Ambani, India’s richest man, is the biggest loser among the country’s billionaires as the rupee’s slump to record lows erased 24 per cent of his fortune.

The chairman of Reliance Industries, operator of the world’s biggest oil refinery complex, has lost $US5.6 billion ($6.2 billion) of his wealth since May 1, as the rupee’s plunge accelerated. The 56-year-old is still left with a net worth of $US17.5 billion, according to the Bloomberg Billionaires Index.

The Indian rupee is the worst-performing major currency in the world in the past month, coming under pressure as international investors sold emerging-market assets amid concern the US will pare its $US85 billion monthly stimulus.

The value of holdings by India’s billionaires are worth less in dollars as the rupee declined and foreign investors sold shares in large-cap companies, said Munesh Khanna, a senior partner at Grant Thornton LLP in Mumbai. ‘‘There is irrationality; the rupee is weak and will go down further,’’ Mr Khanna said.

‘‘Foreign institutional investors are invested in the larger-cap companies and are pulling out money from India. That is putting a lot of pressure on those companies.’’

International investors have sold a net $US3 billion of Indian stocks since June 3, according to the nation’s Securities & Exchange Board.

The S&P BSE Sensex index declined 1.9 per cent to 17,905.91 yesterday, extending its four-day drop to 7.6 per cent, the most since July 2009.

The index was flat in late morning trade today, while the rupee extended its slide, touching an all-time low of 65.13 per US dollar.

Anil Ambani, the younger brother of Mukesh, has lost 17 per cent, or $US1.3 billion, of his net worth since May. Anil Ambani, 54, has a fortune of $US6.3 billion and is the country’s eighth-richest man.

The majority of his wealth is derived from stakes in publicly traded companies, including Reliance Communications, India’s third-largest mobile-phone company by market value.

Reliance Communications reported earlier this month first- quarter profit that missed analysts’ estimates after finance costs increased because of the rupee’s weakness against the US dollar.

‘‘Companies with large foreign-currency debt will feel the pressure and their valuations will come down,’’ Mr Khanna said.

Shares of Reliance Industries, Mukesh Ambani’s most valuable asset, declined about 15 per cent from its 2013 peak on July 19 through yesterday.

The Bloomberg Billionaires Index is a dynamic measure of the world’s wealthy based on changes in markets, the economy and Bloomberg reporting. Each net worth figure is updated every business day at 5.30pm in New York.

Stakes in publicly traded companies are valued using the share’s most recent closing price. Valuations are converted to US dollars at current exchange rates.