Royal Bank of Scotland (RBS) boss Ross McEwan has confessed that the lender has neglected its technology for decades after a system failure left more than one million customers unable to access their accounts.The bank's IT system came under scrutiny after the crash on Cyber Monday, which lasted three hours, on one of the busiest online shopping days of the year.Analysts and banking industry sources say RBS's technology is outdated and made up of a complex patchwork of systems after dozens of acquisitions."For decades, RBS failed to invest properly in its systems," said McEwan, who became Chief Executive in October."Last night's systems failure was unacceptable [...]I'm sorry for the inconvenience we caused our customers," he said, adding he would outline plans in the New Year to improve the bank and increase investment.The latest crash could cost RBS millions of pounds in compensation.Last year the lender experienced a more serious crash in its payments system last year that Britain's regulator is still investigating.Shares were up 0.09% to 331.70p at 15:13 on Tuesday.RD