Non-ministerial government department

Non-ministerial government departments, also called non-ministerial departments (NMDs), are a type of department of the United Kingdom government that deals with matters for which direct political oversight (and thus democratic accountability), through a minister of state forming part of the executive government, has been judged unnecessary or inappropriate. NMDs are typically headed by senior civil servants or subject matter experts.

Source: Wikipedia — Non-ministerial government department (CC BY-SA 4.0)