'Governments can no longer stand idle,' French President Nicolas Sarkozy and British Prime Minister Gordon Brown wrote in an editorial published Wednesday in The Wall Street Journal. The oil price was 'seemingly defying the accepted rules of economics'.

The two leaders called for an international effort to boost transparency and supervision of oil markets. They warned that 'a new period of instability could undermine confidence just as we are pushing for recovery'.

Traders reject the accusations.

They responded that speculators are simply following expectations - prices are climbing because demand is likely to rise as the world economy recovers, especially in developing countries.

CME Group, which owns the New York Mercantile Exchange, argued in a report earlier this year that limiting trader volume will have little effect.

'There's really no substantial evidence that index trader or money manager participation causes increased volatility,' said Dave Lehman, director for commodity research at CME Group.

The possible government clampdown comes amid a wave of new financial regulations being proposed in the US and European Union. Careless risks taken by Wall Street investors - largely in real-estate markets - are blamed for sparking a financial crisis that sent the global economy into a tailspin in October.

US President Barack Obama's administration last month proposed the most sweeping overhaul of financial regulation since the 1930s. The plan would extend the government's reach to virtually all corners of Wall Street and vastly expand the authority of the Federal Reserve to oversee major banks.