The global oil market’s most important pricing benchmark, the West Texas Intermediate crude contract, was criticised on Wednesday for “sending mixed and misleading price signals, not only to the market but to economic forecasters, government officials and policymakers”.

The International Energy Agency warned that “deterioration in the fragile WTI pricing mechanism would only serve to reinforce the view that the crude has become an irrevocably broken benchmark”.

The damning verdict on the WTI contract, which is traded on the New York Mercantile Exchange, by the energy watchdog of the developed world reflects concerns among analysts, traders and investors in commodity indices.

The spread between WTI and Brent, the European benchmark, which is increasingly seen as more representative of global market conditions, was trading at more than $7 a barrel on Wednesday, after reaching a peak of $10.06 on January 15.

Historically, WTI trades at a premium of between $1.50 and $2.50 a barrel to Brent.

Mike Wittner, global head of oil research at Société Générale, said: “Brent is more representative of the global market right now and the disconnect between WTI and Brent is an issue. However, there are different grades of crude available for hedging purposes and other parts of the WTI curve where the price is much higher and less distorted than the front month.”

The front-month WTI contract has come under pressure because of weak US demand, increasing supplies from Canada and rising crude stocks at Cushing, Oklahoma, a hub in the US distribution network.

Stocks at Cushing rose to 34.9m barrels on Wednesday, meaning its operational capacity, estimated at 36m barrels, is in effect full. Almost all pipelines flow one way into Cushing, leaving no outlet to move crude south to refineries along the Gulf of Mexico coast.

The IEA said that, short of building a link to the coast, Nymex could alleviate problems by designating a second delivery point and increasing the number of crudes that met the contract specification. Nymex was not available for comment.

“What the IEA is suggesting is sensible,” said Ed Morse, managing director at LCM Commodities. “It’s urgent for Nymex to act. Look at what is happening in the market right now [following the latest US inventories data]: Brent is rising and WTI is falling. Brent is a reflection of the real world and WTI is reflecting conditions at Cushing.”

Mr Wittner said that if WTI’s open interest [active positions] declined, suggesting traders were losing faith in the contract as a hedging tool, that would “concentrate minds” at Nymex.

He noted that WTI’s open interest had stabilised and there was “no sense at all of any widespread rush for the exit”.