In the earlier institutional set up of national economic planning in India, who, by virtue of office, served as the ex officio Chairman of the Planning Commission?

Introduction / Context:
Before the establishment of NITI Aayog, India had a Planning Commission that was responsible for formulating Five Year Plans and advising on national development priorities. It was an important body in the economic governance of the country. Understanding who headed the Planning Commission as its ex officio Chairman helps you connect the institution with political leadership at the highest level.

Given Data / Assumptions:
- The question refers to the Planning Commission, which has now been replaced by NITI Aayog.- It asks who served as the Chairman of the Planning Commission by virtue of office.- The options are Defence Minister, Attorney General of India, Prime Minister of India and Finance Minister.

Concept / Approach:
The Planning Commission was a non constitutional but important advisory body of the Government of India. By established convention and design, the Prime Minister of India always served as its ex officio Chairman. Other ministers, such as the Finance Minister or ministers in charge of particular sectors, might be members or vice chairpersons, but the top leadership position belonged to the Prime Minister. The Attorney General and Defence Minister never served by default as Chairman.

Step-by-Step Solution:
Step 1: Recall that in discussions about plan documents and Five Year Plans, the Prime Minister was often referred to as the head of the Planning Commission.Step 2: The posts of Deputy Chairman or Vice Chairman were typically given to senior economists or political leaders, but the formal Chairman was the Prime Minister.Step 3: The Defence Minister focuses on national security and armed forces, not on heading the planning body.Step 4: The Attorney General of India is the chief legal advisor to the government and does not chair the Planning Commission.Step 5: The Finance Minister is central to budgetary policy but was not the ex officio Chairman of the Planning Commission.Step 6: Therefore, the correct answer is the Prime Minister of India.

Verification / Alternative check:
You can verify this by remembering that when new governments came to power, the same Prime Minister who headed the Council of Ministers automatically became the Chairman of the Planning Commission. News reports often referred to the Prime Minister chairing its meetings and approving plan documents, which confirms this association.

Why Other Options Are Wrong:
Option A (Defence Minister) is wrong because this minister is responsible for defence policy and is not automatically linked with planning leadership.Option B (Attorney General of India) is wrong as this is a legal advisory post, not a planning or executive office.Option D (Finance Minister) is wrong because, although the Finance Minister plays a key role in implementing plans through budgets, the Planning Commission's chairmanship was always with the Prime Minister.

Common Pitfalls:
A common mistake is to assume that the Finance Minister, being associated closely with economic policy, might have chaired the Planning Commission. Others might think of a separate full time chairperson distinct from the Prime Minister. To avoid this, it is useful to remember the simple rule: Prime Minister = ex officio head of key national bodies like the NITI Aayog (as Chairperson) and earlier the Planning Commission.

Final Answer:
Correct answer: Prime Minister of India