Crude oil prices tumbled on Thursday to a fresh 4 ½ year low, trading as low as $37.70 a barrel, in spite of Opec's historic decision to cut daily production by a record 2.2m barrels a day, which comes on top of the 2m b/d it has already pledged since September.

The bearish reaction also came in spite of further weakness for the dollar, which traditionally boosts dollar-denominated commodities such as oil. The dollar dived to a 10-week low against the euro, down 2 per cent at $1.4719.

The oil price weakness reflected the market's profound doubts about Opec compliance with its own agreement, said Ed Meir of MF Global, the New York-based commodities brokerage.

"The verdict was a resounding vote of no-confidence in the cartel's ability to curtail production given its previous tendencies to backslide on commitments, particularly by countries who are financially strapped", he said.

In morning trading in New York, Nymex January West Texas Intermediate was $2.16 cents lower at $38.90 a barrel. Earlier, it hit a low of $37.71 a barrel, the lowest since July 2004. The January contract expires on Friday.

The Nymew WTI February contract, which will become the market benchmark next week, was $1.50 lower at $43.01 a barrel.

ICE February Brent 55 cents lower to $44.93 a barrel.

Opec said after a policy meeting in Oran, Algeria, that it would cut 4.2m b/d from its September output of 29.045m b/d, bringing its production ceiling to 24.845m b/d in January. The 2.2m b/d agreed on Thursday is the single biggest cut since the cartel created the quota production allocation system in 1982.

Other commodities markets were mixed, with base metals posting heavy losses but agriculture commodities gaining some ground.

On the London Metal Exchange, copper for delivery in three months tumbled 3.9 per cent to $2,929 a tonne, a fresh 4-year low, after a surge in inventories. Copper stocks at LME warehouses rose 2,275 tonnes to 324,175 tonnes, the highest level since early 2004.

Aluminium lost 1.9 per cent to $1,480 a tonne while lead tumbled 4.9 per cent to $954 a tonne. Zinc, nickel and tine also posted losses.

In the agriculture markets, wheat was strong after warnings that farmers in the US and Europe have cut their plantings.

CBOT March Wheat rose 8 cents to $5.65 ½ a bushel, a 6-week high, after both the International Grains Council, a London-based intergovernmental body, and the United Naitons' Food and Agriculture Organisation warned of lower planting for 2009-10.

The IGC said that despite generally favourable northern hemisphere conditions a decline in planting and reduced yields will likely lead to a smaller wheat crop in 2009-10. "Already, early indications for the first of the 2009 crops just sown in some major producing and exporting countries point to area reductions, such as for winter grains (mostly wheat) in Europe and the United States," it said.

CBOT March corn rose 5 cents to $3.94 ½ a bushel while CBOT January soyabean traded 5 ¾ cents higher to $8.69 ¾ a bushel.

Liffe May cocoa in London rose in early trading to a 22-year high of £1,751 a tonne, but later traded 2.6 per cent down to £1,676 a tonne. In New York, ICE May cocoa fell 2.5 per cent to $2,544 a tonne, after touching a 3-month high of $2,679 a tonne on Wednesday.