The city or town shall designate the officer or agency to receive a proposal for adoption, amendment, or repeal of a zoning ordinance or zoning map(s). Immediately upon receipt of the proposal, the officer or agency shall refer the proposal to the city or town council, and to the planning board or commission of the city or town for study and recommendation. The planning board or commission shall, in turn, notify and seek the advice of the city or town planning department, if any, and report to the city or town council within forty-five (45) days after receipt of the proposal, giving its findings and recommendations as prescribed in § 45-24-52. Where a proposal for adoption, amendment, or repeal of a zoning ordinance or zoning map is made by the city or town planning board or commission, the requirements for study by the board may be waived; provided, that the proposal by the planning board includes its findings and recommendations pursuant to § 45-24-52. The city or town council shall hold a public hearing within sixty-five (65) days of receipt of a proposal, giving proper notice as prescribed in § 45-24-53. The city or town council shall render a decision on any proposal within forty-five (45) days after the date of completion of the public hearing. The provisions of this section pertaining to deadlines shall not be construed to apply to any extension consented to by an applicant.