51. (1) Subject to this section, any trade dispute, not otherwise determined or resolved may be reported to the Minister only by—
(a) the employer;
(b) the recognised majority union;
(c) where there is no recognised majority union, any trade union, of which the worker or workers who are parties to the dispute are members in good standing,
The time limits for reporting a trade dispute are set out in Section 51(3) which also has a provision that the reporting parties party can ask for an extension of time if they are over the six months.
51. (3) A trade dispute may not be reported to the Minister if more than six months have elapsed since the issue giving rise to the dispute first arose, save that the Minister may, in any case where he considers it just, extend the time during which a dispute may be so reported to him.
Any union can take up what are called "rights" issues. Only an Recognised Majority Union can take up "interest" issues.
A "rights" issue is one concerning the existing rights a worker has and these would normally be found in the contract of employment, a collective agreement (if there is one) or the law.
An "interest" dispute" one concerning collective bargaining issues (such as a breakdown in negotiations) which is something that only a Recognised Majority Union can take up.
The legal description of these differences is set out in Section 51(5):
51. (5) For the purpose of this Act and in particular subsection (1)(c), a trade union other than a recognised majority union, is competent to pursue the following types of trade dispute, but no other, in accordance with this Act:
(a) any dispute or difference between the employer and the union or between workers and workers of that employer, in each case being on behalf of members of the union, concerning the application to any such worker of existing terms and conditions of employment or the denial of any right applicable to any such worker in respect of the employment; and
(b) a dispute between the employer and the union as to dismissal, employment, non employment, suspension from employment, refusal to employ, re-employment or reinstatement of a worker or workers.