Prime Minister as the head of Government plays a crucial role in the political, administrative system the country.
To fulfill his responsibilities he is assisted by PMO. PMO is a staff agency meant f providing secretarial assistance and crucial advice to the PM.
It is an extra constitutional body a enjoys the status of a department of Government of India under the allocation of business rules 1961 PMO came into existence in 1947 by replacing the secretary to the Governor General (Personal).
PM is headed by PM and administrate by the Principal Secretary. Additionally it consists of one or t additional secretaries, 3-5 joint secretaries and number of directors, deputy secretaries/ under secretary