Washington, D.C. ? The resignation of the No. 2 man at the Homeland Security Department is the latest sign of churn at the highest reaches of the beleaguered bureaucracy charged with protecting the homeland.

Deputy Homeland Security Secretary Michael P. Jackson, who oversees the agency’s day-to-day operations, notified colleagues by e-mail Monday that he will resign Oct. 26.

“I am compelled to depart for financial reasons that I can no longer ignore,” he said in the e-mail. Jackson makes $168,000 a year in a job he has held since March 2005.

Jackson’s departure comes amid growing concerns about turnover at the sprawling agency of 180,000 employees, especially in the final 16 months of a lame-duck administration. In its 4 1/2-year history, the fledgling agency has had two secretaries, three deputy secretaries, two undersecretaries for management and two chief financial officers – most of whom left for bigger paychecks in the private sector.