If the Controller, after giving the tenant a reasonable opportunity of showing cause against the applicant, is satisfied (ii) that the tenant has after the commencement of this Act without the written consent of the landlord (a) transferred his right under the lease or sublet the entire building or rented land or any portion thereof; or 176 (b) used the building or rented land for a purpose other than that for which it was leased, or the Controller may make an order directing the tenant to put the landlord in possession of the building or rented land and if the Controller is not so satisfied he shall make an order rejecting the application: Provided that the Controller may give 'the tenant a reasonable time for putting the landlord in possession of the building or rented land and may extend such time so as not to exceed three months in the aggregate." Shri Mahajan contended that to constitute the ground under section 13(2) (ii) (b), the change in user should be in respect of at least a substantial part of the building if not the entire building.