The head of the U.S. nuclear security agency has been forced to resign over management and security issues at the Los Alamos National Laboratory.

Secretary of Energy Samuel Bodman asked for the resignation of Linton Brooks, administrator of the National Nuclear Security Administration late last week. Issues, including a "serious security breach" at the Los Alamos lab, led to the move.

Bodman said outstanding issues surrounding the security breach had not been addressed adequately.