18. Authorisation of representative and appointment of legal practitioner

An authorisation given under rule 17 or an appointment of a legal practitioner by a dealer or other person to represent him in any proceedings before any authority under the Act, other than the High Court shall be valid for the purpose of appearance before such authority, until it is cancelled in writing: Provided that if the dealer or other person desires to cancel the appointment of the legal practitioner or the said authorisation in the course of the proceedings before any such authority, he may do so with the consent of the legal practitioner, or the Chartered Accountant, or the Cost Accountant or the Value Added Tax practitioner, so authorised or if such consent is refused, with the permission of the said authority.