6. Leave on trade union business.
A workman intending to carry out his duties or to exercise his rights as an officer of a trade union shall apply in writing to his employer for leave of absence stating the durations of and the purposes for which such leave is applied for and the employer shall grant the application for leave if the duration of the leave applied for is for a period that is no longer than what is reasonably required for the purposes stated in the application:
Provided that a workman shall not be entitled to leave with pay for the duration of his absence if the purposes for which he is absent from work are not to represent the members of his trade union in relation to industrial matters concerning his employer.