4.—(1) In this section “agreement” means an agreement, whether a contract of employment or not, and whether made before or after the commencement of this Act.

(2) A provision in an agreement shall be void in so far as it purports to exclude or limit the application of any provision of this Act or is inconsistent with any provision of this Act.

(3) A provision in an agreement which is or becomes less favourable in relation to an adopting parent than a similar or corresponding entitlement conferred on F17[the adopting parent] by this Act shall be deemed to be so modified as to be not less favourable to F17[the adopting parent].

(4) Nothing in this or any other enactment shall be construed as prohibiting the inclusion in an agreement of a provision (subsequently referred to in this section as “the additional provision”) in relation to adoption, in addition to those required by this Act, the effect of which would be to render the agreement more favourable to an adopting parent than it would be if it did not include the additional provision.

(5) The inclusion of the additional provision in an agreement shall not, by reason of the fact that it applies to an adopting parent only, confer any right under this or any other enactment on an employee who is not an adopting parent.