5. The Department of the Environment may confirm, with or without modifications, or refuse to confirm, any bye-law submitted for confirmation, and subject to the proviso in paragraph 2 may fix the date on which the bye-law is to come into operation and subject as aforesaid if no date is fixed the bye-law shall come into operation at the expiration of one month from the date of its confirmation;
Provided that where the Department of the Environment proposes to confirm a bye-law with a modification which appears to it to be substantial it shall inform the district council and require the district council to take any steps it considers necessary for informing persons likely to be concerned with the modification and shall not confirm the bye-law until such period has elapsed as it thinks reasonable for consideration of, and comment upon, the proposed modification by the district council and by other persons who have been informed of the modification.