The US derivatives regulator has revealed that speculators control more than four-fifths of oil contracts on the nation's main commodity futures exchange, far more than was previously thought, after repeatedly playing down the effect of speculation on soaring oil prices.

The Commodity Futures Trading Commission said financial firms speculating for their clients, or for themselves, accounted for about 81% of the oil contracts on the New York Mercantile Exchange, according to the Washington Post. That share may rise as the regulator checks the status of other big traders, the newspaper said.