NEW YORK: Shell and Exxon Mobil have overtaken Walmart to become the world's biggest companies by revenue, a report from Fortune, the business title, has shown.

Shell, the Anglo-Dutch oil group, led the charts, having seen revenues rise by 28.1% in 2011 to $484.5bn. Exxon Mobil, its rival, was second with its revenues increasing by 27.7% to $452.9bn.

Walmart, the retailer, took first place in each of the last two years but only claimed third in 2012, even though sales rose by 6% to $446.9bn. One reason for this was slowing demand at home, as "executives found it harder to lure US shoppers."

"Beyond sales, the chain also struggled with a shaky public image," the study added, as a Supreme Court case - ultimately rejected - accusing Walmart of favouring men over women in the area of pay and promotions, and allegations of bribery involving its Mexican arm kept the firm in the headlines.

BP, in fourth, grew revenues by 25.1% to $386bn, after facing reputational damage of its own following the Deepwater Horizon oil spill in the Gulf of Mexico two years ago, leading to a $3.3bn loss in 2010.

"We remained mindful of the tragic events seen in 2010 and the need to ensure such an accident never happens again," Carl-Henric Svanberg, its CEO, wrote in a letter to shareholders. BP has thus prioritised safety, assisting with the clean-up operation and improving cashflow.

Three Chinese companies came next: Sinopec and China National Petroleum, two further energy conglomerates, on $375.2bn and $352.3bn respectively, and State Grid, the power firm, on $259.1bn.

Indeed, in the last decade, the amount of Chinese enterprises featuring among the 500 biggest players has more than doubled, now standing at 73, with Brazil's representation also increasing from four to eight.

During the same period, the number of American organisations in the rankings has declined from 197 to 132 today, with Japan off from 88 to 68.

Elsewhere, the most profitable corporation on the list was Gazprom, the Russian gas firm, which netted $44.5bn, ahead of Exxon Mobil on $41.1bn.

The Industrial and Commercial Bank of China, the financial services provider, generated $32.2bn, beating Shell on $30.9bn.

Apple, the electronics pioneer, was the first member of this group to fall outside the energy and financial sectors, in seventh on this metric with $25.9bn. Microsoft, the IT giant, occupied tenth on $23.2bn.

Data sourced from Fortune; additional content by Warc staff