Who may propose the registration of an initiative?

Republic Act No. 6735 'The Initiative and Referendum Act'

http://www.chanrobles.com/republicactno6735.htm#.UMhZ8Gd32uI

Sec. 5. Requirements. — (a) To exercise the power of initiative or referendum, at least ten per centum (10%) of the total number of the registered voters, of which every legislative district is represented by at least three per centum (3%) of the registered voters thereof, shall sign a petition for the purpose and register the same with the Commission.

(b) A petition for an initiative on the 1987 Constitution must have at least twelve per centum (12%) of the total number of registered voters as signatories, of which every legislative district must be represented by at least three per centum (3%) of the registered voters therein. Initiative on the Constitution may be exercised only after five (5) years from the ratification of the 1987 Constitution and only once every five (5) years thereafter.

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Sec. 11. Indirect Initiative. — Any duly accredited people's organization, as defined by law, may file a petition for indirect initiative with the House of Representatives, and other legislative bodies. The petition shall contain a summary of the chief purposes and contents of the bill that the organization proposes to be enacted into law by the legislature.

The procedure to be followed on the initiative bill shall be the same as the enactment of any legislative measure before the House of Representatives except that the said initiative bill shall have precedence over the pending legislative measures on the committee