A dispute has arisen regarding admission of membership of a union which is a registered and recognised trade union. Few workers had filed a joint application for membership of that union. The application was not considered because the application was not in accordance with the procedure laid down by the union. Aggrieved by this, the workers filed a complaint before the Registrar of Trade Unionsunder Section 28 (1-A). Which one among the following is competent authority to settle the issue?