What role did speculators play in driving the oil price to record highs last summer?

More than the authorities were initially willing to admit, if the Commodity Futures Trading Commission is anything to go by.

In a major U-turn, the US regulator will next month publish a report suggesting speculators played a significant role in driving wild swings in the oil price, having previously claimed it was all down to supply and demand.

CFTC commissioner Bart Chilton reckons the early analysis was based on "deeply flawed data" and is now calling for a clampdown on speculative trading and in particular limits on speculative trading on energy futures contracts.

"I believe we're going to do something," said Chilton.

"I would be extremely surprised if we don't take some action to set hard limits."

Tighter regulation will no doubt hit profits at energy trading firms such as that run by Andrew Hall.

He is head of Citi's highly profitable energy-trading unit Phibro and could get paid as much as $100 million (£61 million) this year.

But it is seen as a must by many politicians who worry that rising oil prices could prolong the global recession.

Futures contracts were traditionally used by producers and consumers who sought to hedge against oil-market volatility and in doing so reduced that volatility.

However, speculators have invested hundreds of billions of dollars in the contracts, using them to bet on market prices, which critics say magnify the price swings.

Opec has long blamed speculators for price volatility - often, it is claimed, to distract from the fact that it can cut supply to support the oil price when it chooses.

But there has long been a reluctance to address the situation for fear of damaging the free market.

Intense lobbying by a financial industry bent on making a killing out of wild price swings has influenced legislators and regulators alike.

With a change of administration in the White House, talk of tighter regulation is back on.

But there is no united front. Even in the UK, Prime Minister Gordon Brown talks of taking action to curb "dangerously volatile" oil prices while the Financial Services Authority is thought to have found little evidence to suggest speculators are behind the big price swings of recent years.