The spot oil prices fell 5pc overnight on Thursday, to a five-year low of $US35/barrel, on the New York Mercantile Exchange.
In London, the February Brent crude contract also fell 5pc on the ICE Futures exchange.
This fall comes on top of a US report which shows US petroleum demand fell by 6pc in 2008, according to the American Petroleum Institute.
That falling trend in US oil use appears to be continuing this year, with millions of people now out of work, the institute says.
World-wide, trucking companies also have seen a big drop in business as orders dry up.
With the economic slowdown, many of the world’s crude storage tanks are full as the stockpile rises, with tighter storage space concerns contributing to the downwards pressure on oil prices.
US oil stockpiles, in particular, have been rising, especially in the second half of 2008.