washington head u.s. internal revenue service resign due agency inability improve defenses hack taxpayer data republican lawmaker say friday republican representative barbara comstock say new leadership need replace irs commissioner john koskinen due failures secure americans sensitive information malicious intrusions escalate line attack republicans frequently criticize federal tax collection service commissioner koskinen provide little confidence cyber security top priority irs comstock say statement share reuters add concern agency apparently one charge cyber security irs immediately comment 700,000 individuals may personal information pilfer hackers intrusion last year irs announce february number repeatedly revise upward initial estimate far small comstock statement cite government accountability office report release last month find irs struggle upgrade information security plan irs agree work toward implement dozens outline recommendations koskinen appear congressional committees week say comply gao recommendations priority commissioner near-constant fire republicans since take agency 2013 amid controversy whether irs target conservative group 60 republicans sign resolution introduce october impeach koskinen charge impede congressional investigation irs treatment conservative group comstock first lawmaker call koskinen resignation solely cyber security reason aide say koskinen first obama administration official target congress handle cyber security last year katherine archuleta head office personnel management resign several lawmakers party call ouster follow theft personal data 21 million individuals comstock say friday koskinen follow lead archuleta top executives leave due poor handle hack allow new trust leadership irs u.s. lawmaker call irs chief resign handle hack data