washington -- James Byrne, second in command at the embattled Office of Special Counsel, resigned his post effective today after leaving his boss, Scott J. Bloch, a stinging letter suggesting that Bloch's "political agendas and personal vendettas" were preventing the agency from fulfilling its mission.

The two-paragraph letter, obtained by The Times, was sent to Bloch last week at a time when the Bush appointee faces a Justice Department inquiry that includes allegations of illegally erasing information on his government computer. James Mitchell, a spokesman for the independent agency, declined to comment on the matter.