(6)If, in the case of any marketing scheme for the time being in force which is a scheme for regulating, in any respect, the carrying on of two or more designated businesses, a request for a poll on the question whether or not the scheme should be revoked is made in writing to the board administering the scheme by or on behalf of the prescribed number of persons registered under the scheme as carrying on a particular designated business, the board shall forthwith communicate the request to the Commission, and thereupon the Commission shall cause to be taken in the prescribed manner a poll of persons registered under the scheme as carrying on that business, and shall communicate the result of the poll to the Ministers; and if the result of the poll shows that not less than half of the total number of votes polled have been cast in favour of revocation of the scheme, the Ministers shall by order revoke the scheme :
Provided that no poll of persons registered under the scheme as carrying on a particular designated business shall, without the consent of the board, be taken under this subsection—
(a)within the two years immediately following the date on which the order confirming the scheme was made; or
(b)within such period after the date of the declaration of any previous poll of persons registered under the scheme as carrying on that business, being a poll taken under this subsection in relation to the scheme, as may be specified in the scheme.