(1)A local planning authority may at any time, and shall if so directed by the Secretary of State, make proposals for the alteration or replacement of a unitary development plan adopted or approved for their area under the previous provisions of this Chapter but, except in pursuance of such a direction, a local planning authority shall not without the consent of the Secretary of State make proposals under this section in respect of any plan or part of a plan if that plan or any part of it has been approved by him under those provisions.
(2)Subject to section 22, sections 12 to 20 (other than subsection (1) of section 12) shall apply in relation to the making of proposals under this section and to any alteration or replacement so proposed as they apply to the preparation of a unitary development plan under section 12 and to a plan prepared under that section.
(3)As soon as practicable after—
(a)an order has been made under paragraph 5 of Schedule 32 to the [1980 c. 65.] Local Government, Planning and Land Act 1980 (designation of enterprise zone); or
(b)a notification has been given under paragraph 11(1) of that Schedule (approval of modification of enterprise zone scheme),
the local planning authority for an area in which the zone is wholly or partly situated shall review any unitary development plan for that area in the light of the provisions of the scheme or modified scheme under that Schedule and prepare proposals under this section for any consequential alterations to the plan which they consider necessary.