Dear dipaknsk
Welcome to CiteHR.
To get better and complete solutions to your queries, you must furnish all relevant information of your organisation, the law/Acts applicable, location, size, type of business activity etc.
Whether it is a union leader or an employee; I trust that you must be having a provision/list of "misconducts" in your Standing Order, Conduct & Discipline rules, Code of Ethics etc. to deal with the situation.
Warm regards.