The litigation background-

1. Petitioner No.1, Municipal Corporation of Greater Mumbai (for short, “Corporation”) is a statutory authority established under the provisions of the Mumbai Municipal Corporation Act, 1888 (for short, the MMC Act). The Petitioners are under various obligations to discharge their duties and functions, through its employees/workers. Petitioner No.1 is a “Local Body”/ “Authority”/“Employer” to provide public services, all sorts of Civil amenities and for smooth and proper function and to maintain all essential services/facilities, they appoint various types of employees for the respective Departments. Both are governed by their employment contract and related laws. The Petitioner-Corporation, for these activities, has more than 145000 employees, including permanent, seasonal and daily employees, excluding part timers. It has more than 1000 designations and more than 50 and odd related pay-scale grading wages and related benefits.

2. Respondent No.1 (Municipal Mazdoor Union) (for short, “MMU”) is one of the leading recognized Union among the other 36 unions of the employees of the Corporation. The Respondent's Union along with other affiliated uni