Senator Bernie Sanders handed the Wall Street Journal names and positions of traders covering the run up to a period of record oil prices in 2008 before posting the documents on his Web site.

The data was initially gathered by the Commodity Futures Trading Commission in 2008 but an internal investigation has found no evidence that a member of its staff was responsible for handing it to Sanders.

According to Reuters, citing people familiar with the matter, the information was formally requested by the US House Energy Committee - which the CFTC has to comply with - but then made its way to the Senate and Sanders.

Explaining his decision to leak, Sanders says: "This report clearly shows that in the summer of 2008 when gas prices spiked to more than $4 a gallon, Goldman Sachs, Morgan Stanley, and other speculators on Wall Street dominated the crude oil futures market causing tremendous damage to the entire economy. The CFTC has kept this information hidden from the American public for nearly three years. That is an outrage."

In a letter to CFTC chairman Gary Gensler, the FIA says "this unfortunate incident poses a serious threat to the confidence of market participants in the CFTC's ability to protect propriety information; raises troubling questions about the role of Congress in handling such information; jeopardises the CFTC's future ability to obtain cooperation in data collection and market surveillance".

With Dodd-Frank giving the CFTC greater authority to collect proprietary data on customer positions, the FIA is calling for a full investigation, arguing that "a complete understanding of what transpired and which laws, if any, were broken is essential to restoring confidence in the confidentially of information shared with the CFTC".