Whenever any town shall, by ordinance, provide for the appropriation, purchase or leasing of private property for the purposes aforesaid and the value of such property, or the rental thereof, shall alone, or when added to the amount of liability incurred for any of the purposes aforesaid, within the preceding three years exceed one and one-half mills on the dollar of valuation as provided in the preceding section and the question of the increase of indebtedness of the town for any of said purposes has not been submitted to, and assented to, by a majority of the electors voting on such question at an election held for the purpose of obtaining such assent according to law, the council shall cause the question of such appropriation, purchase or leasing to be submitted to the electors of the town at an election to be held at the places of holding elections in said town on a day to be fixed by council which shall be the day of a general, municipal or primary election.