Section 6D. Section six C shall be submitted for acceptance to the registered voters of a city at a regular city election if the city council thereof so votes, and of a town at an annual town election upon petition of two hundred registered voters or of twenty per cent of the total number of registered voters, substantially in the form of the following question, which shall be placed on the official ballot used for the election of officers at such city or town election:

If a majority of the votes in answer to said question is in the affirmative, then said section shall thereupon take full effect in such city or town, but not otherwise.