Barclays' key investment bank arm ended 2011 with its worst quarter for three years as the eurozone debt crisis hit bond trading, dragging the British bank's annual profit down.

Britain's fourth-biggest bank by market value has reported a pretax profit of £5.9bn for 2011, down 3 percent on the year and below analysts' forecast of £6.1bn.

Income at investment bank arm Barclays Capital fell to £1.8bn in the fourth quarter, down 19 percent on the previous three months.