Brent crude oil fell almost $2 a barrel on Monday to a new five-year lows on predictions that oversupply would keep building until next year after OPEC decided not to cut output.
"Without OPEC intervention, markets risk becoming unbalanced, with peak oversupply likely in the second quarter of 2015," Morgan Stanley analyst Adam Longson said.
In a report dated December 5, the US investment bank said oil prices could fall as low as $43 a barrel next year. The bank cut its average 2015 Brent base case outlook by $28 to $70 per barrel, and by $14 to $88 a barrel for 2016.
Brent crude for January was down $1.45 cents at $67.62 a barrel by 1000 GMT, having fallen $1.72 to $67.35 - its lowest since October 2009.
US crude was down $1.16 cents at $64.68 a barrel, after hitting a session low of $64.63. The US contract, also known as West Texas Intermediate, touched $63.72 last week, its lowest since July 2009.
At a meeting last month, top oil exporter Saudi Arabia resisted calls from poorer members of the Organization of the Petroleum Exporting Countries to reduce production, fuelling a further slide in prices, which have lost more than 40 per cent since June.
"Brent is moving into the $60 to $70 trading range," said Olivier Jakob, oil analyst at Petromatrix in Zug, Switzerland.
"There is nothing really providing strong support for crude oil right now," he added.
Mixed Chinese trade data further unsettled prices.
China's imports shrank unexpectedly in November, falling 6.7 per cent, while export growth slowed, fuelling concerns the world's second-largest economy could be facing a sharp slowdown.
China's crude oil imports rose 9 percent in November from October to 6.18 million barrels per day, suggesting the country may be boosting its reserves.
"If one looks at the overall economic indicators, they are all showing a picture of China which is stagnating rather than having strong growth," said Jakob.