The NDP says it will propose legislation that would make it harder for Ontario to make changes to municipalities.
The bill would require the government to give public notice, conduct consultations and get the approval of municipalities before cutting the size of their councils, changing their wards or amalgamate or dissolve them.
The provincial government cut the size of Toronto city council last year and is reviewing the structures of regional governments, including Niagara's.
The region is under review, along with a number of other two-tier municipalities.
Private member's bills rarely get turned into law.