Dear Meenu,
Our learned friend Saswat has provided a correct answer to your query, albeit a bit briefly. Hence, I believe that for the sake of better understanding, it needs to be elaborated with reference to the definition of the term "industrial dispute" as defined under Section 2(k) of the Industrial Disputes Act, 1947.
If you critically analyze the term, you will find that it comprises three parts. The first part crisply defines a dispute as a difference. The second part mentions the parties to the dispute; the dispute can be between workmen and employers, or between workmen and workmen, or between employers and employers. The third part specifies the subject matter of such a dispute between the mentioned parties. It can be connected with employment or non-employment, the terms of employment, or the conditions of labor of any person. Here, the term "any person" refers not to all and sundry but only to that person in whom the parties have a community of interest.
Applying the above principles, we can conclude that even though the trade union issue mentioned is a dispute between workmen, the subject matter is entirely different. Therefore, it is not an industrial dispute to be resolved under the provisions of the Industrial Disputes Act, 1947, but merely a civil dispute to be resolved by a Civil Court.