Explanation:

The Constitution does not lay down the member of Ministers that may constitute the Council of Ministers. The Prime Minister is free to appoint, as many Ministers (maximum of 15% of total strength) as may be deemed necessary. All the members of the Council of Ministers do not belong to the same rank. The Constitution does not classify ministers into different ranks but in practice 4 ranks have come to be recognized.

I. Cabinet Ministers—He has a right to be present and participate in every meeting of the Cabinet. For proclamation of an emergency under Art. 352 the advice must come from the Prime Minister and other Ministers of cabinet rank.

II. Minister of State with independent charge—He is a Minister of State who does not work under a Cabinet Minister. When any matter concerning his Department is on the agenda of the Cabinet, he is invited to attend the meeting.

III. Minister of State—He is a Minister who does not have independent charge of any Department and works under a Cabinet Minister. The work to such Minister is allotted by his Cabinet Minister.

IV. Deputy Minister—He is a Minister who works under a Cabinet Minister or a Minister of State with independent charge. The work to him is allotted by the Minister under whom he is working.
The Prime Minister allocates portfolios to the Cabinet Ministers and Ministers of State with independent charge. The other Ministers are allocated work by their respective Cabinet Ministers.

Ministers may be chosen from the Lok Sabha or the Rajya Sabha. A Minister who is member of one House has the right to speak and to take part in the proceedings of the other House. A Minister is allowed to vote only in the House of which he is a member. A person who is not a member of either House may also be appointed as a Minister. He can continue as a Minister only for six months. Because that is the limit fixed by Art. 75(5). If he desires to continue as Minister he has to become a member of any one of the Houses of Parliament before the expiration of the period of 6 months.

A person who is not qualified to become a member of a legislature cannot be appointed a minister under Art. 75(5). In this case minister would not include Prime Minister because non-election of Prime Minister would dissolve the Council of Ministers after expiration of the period of 6 months.