A revised determination of entitlement to a supplementary welfare allowance made by a designated person shall take effect as follows:

(a) where any supplementary welfare allowance will, by virtue of the revised determination be disallowed or reduced and the revised determination is given owing to the original determination having been given, or having continued in effect, by reason of any statement or representation (whether written or verbal) which was to the knowledge of the person making it false or misleading in a material respect or by reason of the wilful concealment of any material fact, it shall take effect from the date on which the original determination took effect, but the original determination may, in the discretion of the designated person, continue to apply to any period covered by the original determination to which the false or misleading statement or representation or the wilful concealment of any material fact does not relate;

(b) where any supplementary welfare allowance will, by virtue of the revised determination, be disallowed or reduced and the revised determination is given in the light of new evidence or new facts (relating to periods before and after the commencement of this Act) which have been brought to the notice of the designated person since the original determination was given, it shall take effect from the date that the designated person shall determine having regard to the new facts or new evidence and the circumstances of the case;