HSBC's private banking arm is facing charges of tax fraud by Belgium authorities.The Switzerland-based bank is accused of enabling more than 1,000 Belgians dodge taxes by transferring money to offshore tax havens.Brussels authorities said the bank had "knowingly eased and promoted fiscal fraud by making offshore companies available to certain privileged clients".It said these companies existed solely to aid tax avoidance.HSBC said it would "continue to cooperate to the fullest extent possible".