Oil sank below the key level of $50 a barrel this week for the first time in more than three years, as commodity markets continued to slide amid grim forecasts for a prolonged global recession.

Nymex January West Texas Intermediate managed to finish 51 cents higher at $49.93 a barrel yesterday, but was still down 12.5 per cent on the week. ICE January Brent rose $1.11 to $49.19 yesterday, but was also down 14.6 per cent this week.