126. (a) This Constitution shall not be altered except in the following manner: The Bill for the alteration thereof must be passed by an absolute majority of each House of Parliament, and not less than two· nor more than six months after its passage through both Houses of Parliament, shall be submitted to the Provincial Legislatures.But if either House of Parliament passes any such Bill by an absolute majority, and the other House rejects or fails to pass it, or passes it with any amendment to which the first-mentioned House will not agree, and if after an interval of three months the first-mentioned House, in the same or the next session, again passes the Bill by an absolute majority with or without any amendment which has been made or agreed to by: the other House, and such other House rejects or fails to pass it or passes it with any amendment to . which the first-mentioned House will not agree, the Viceroy may submit the· Bill as last proposed by the first mentioned House, and either with or without any amendments subsequently agreed to by both Houses, to the Provincial Legislatures. If in a majority of the Provinces a majority of the members of the Provincial Legislatures voting on the subject after the next general election, at which the issue shall be specially raised, approve the Bill, and if a majority of all the members of the Provincial Legislatures voting also approve the Bill, it shall be presented to the Viceroy for His Majesty’s assent.
(b) No alteration diminishing the proportionate representation of any Province in either House of Parliament or the number of representatives of a Province in the Legislative Assembly, or increasing or diminishing or otherwise altering the limits of a Province, or in any manner affecting the provisions of the Constitution in relation thereto, shall become law unless the majority of the members of the Provincial Legislature voting on the Bill approve it. Provided however that an alteration of the Constitution in relation to a single Province only shall be referred, subject to the provisions of the foregoing Sections, to the Legislature of the Province concerned and be decided by an absolute majority of the members.