LONDON, Feb. 25 -- HSBC's two top executives Wednesday apologized for its Swiss unit's "unacceptable" practice on dodging tax for its clients.

Stuart Gulliver, group chief executive of HSBC, said the practices had caused "damaged to trust and confidence" in the company.

Gulliver and Douglas Flint, chairman of HSBC, were answering questions from British Members of Parliament (MPs) of the House of Commons Treasury Committee.

Earlier this month, the Britain-based bank was reported its Swiss private bank helped clients to evade tax.

The two executives have already delivered their apologies on the misconducts via advertised page of British newspapers and its yearly financial statement report afterward.

Gulliver said: "I'd like to put on the record an apology for the unacceptable events that took place at our private bank in Switzerland in the mid-2000s, which is clearly an apology we'd like to make to you all, to our customers, shareholders, to the public at large."

He stressed: "It clearly was unacceptable and it has clearly damaged HSBC's reputation."

Stuart Gulliver has worked for HSBC for 35 years. He was appointed as group chief executive in 2011.

Flint, who was financial director of HSBC when the case happened, said he felt shamed and would take his "share of responsibility" for Swiss unit failings.

He also emphasized that the process of reforming or restructuring the bank will "always be ongoing", and now it is "more than half way".