An adoption order shall not be made unless—
(a) the child is free for adoption by virtue of an order made
(i) in England and Wales, under section 18;
(ii) in Scotland, under section 18 of the Adoption (Scotland) Act 1978; or
(iii) in Northern Ireland, under Article 17(1) or 18(1) of the Adoption (Northern Ireland) Order 1987.; or
(b) in the case of each parent or guardian of the child the court is satisfied that—
(i) he freely, and with full understanding of what is involved, agrees unconditionally to the making of an adoption order (whether or not he knows the identity of the applicants), or
(ii) his agreement to the making of the adoption order should be dispensed with on a ground specified in subsection (2).
The grounds mentioned in subsection (1)(b)(ii) are that the parent or guardian—
(a) cannot be found or is incapable of giving agreement;
(b) is withholding his agreement unreasonably;
(c) has persistently failed without reasonable cause to discharge his parental responsibility for the child;
(d) has abandoned or neglected the child;
(e) has persistently ill-treated the child;
(f) has seriously ill-treated the child (subject to subsection (5).
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Agreement is ineffective for the purposes of subsection (1)(b)(i) if given by the mother less than six weeks after the child’s birth.
Subsection (2)(f) does not apply unless (because of the ill-treatment or for other reasons) the rehabilitation of the child within the household of the parent or guardian is unlikely.