The boss of Swiss bank Credit Suisse has said he deeply regrets that some of its bankers violated US tax laws. But the Chief Executive of bank Brady Dougan said in a statement to a US Senate committee that there is only scattered evidence of improper conduct. A US Senate report alleged the bank had helped US clients hide billions of dollars from the US taxman. Mr Dougan admitted some private bankers had helped Americans hide income and assets to illegally avoid US tax.