US regulators on Thursday revealed a wide-ranging investigation into crude oil trading practices amid increasing Congressional concern over the role of speculators in record energy prices.

The Commodity Futures Trading Commission, US futures watchdog, said it had decided to break the customary secrecy surrounding enforcement actions because of “today’s unprecedented market conditions”. It said it had been investigating “the purchase, transportation, storage, and trading of crude oil and related derivative contracts” since December 2007.