Any action engaged in by a public employer, its representatives or agents, or by an employee organization, its representatives or agents, which discriminates between nonmembers who pay the said representation fee and members with regard to the payment of such fee other than as allowed under this act, shall be treated as an unfair practice within the meaning of subsection 1(a) or subsection 1(b) of this act.
N.J.S. § 34:13A-5.7