The price of oil has fallen below $35 per barrel for the first time since July 2004, following a brief recovery on Monday.
The price of Brent crude oil dropped 3.7% to as low as $34.83 a barrel, before covering slightly at $35.07. US crude oil fell 2.5% to $35.07 per barrel.
Prices initially rose by around 3% on Monday as growing diplomatic tensions between Saudi Arabia and Iran sparked concerns over future oil supplies. But analysts say those fears have now subsided.
Oil prices had been at around $110 per barrel between 2010 and mid-2014. But over supply sparked a huge fall from the summer of 2014, with prices remaining low throughout 2015.