He told the Sunday Telegraph that descriptions of the industry as "casino banking" have no basis in reality.
"These are real, client-driven businesses," said Mr Diamond. "We are providing services to corporate clients, to fund managers, to retail clients through branch banking and high net-worth banking."
British business secretary Vince Cable has criticized the recent appointment of Mr Diamond to Barclays' top job, stating his concern that the investment banker should be put in charge of retail operations.
But Mr Diamond said it is not accurate to label Barclays as a casino operation, especially as it closed down its proprietary trading unit in 1998.
Mr Diamond is to take over from John Varley in the chief executive's role from March 31st 2011, with Mr Varley acting in an advisory capacity to the bank until September of next year.
By Tony Aynsley