UK bank Barclays on Friday said its 2011 full-year net profit slumped as the bank pushed back a key growth target after a sharp drop in investment banking revenue.

The London-based bank said net profit for 2011 fell 15.6% to £3bn. Adjusted return on equity, a closely watched metric among investors and analysts, fell to 6.6% from 6.8% a year earlier, well below the bank's 2013 target of 13%. Barclays chief executive Bob Diamond said the bank's 2011 return on equity was "unacceptable" and warned that the 13% target might not be achieved by 2013.