Local authorities are subject to a general duty in carrying out their functions, to make arrangements for ensuring that:
(a) their functions are discharged having regard to the need to safeguard and promote the welfare of children; and
(b) any services provided by another person pursuant to arrangements made by the person or body in the discharge of their functions are provided having regard to that need:

Children Act 2004, s.11(2)
Section 11 does not define “welfare”, but section 10 provides a statutory framework for co-operation between the local authority and relevant agencies with a view to improving the “well-being” of children in the area. Well-being for this purpose is defined as (a) physical, mental and emotional well-being; (b) protection from harm and neglect; (c) education, training and recreation; (d) the contribution made by children to society; and (e) social and economic well-being (section 10(2) ). The welfare of the child has long been given a broad meaning in family proceedings, encompassing physical, psychological, social, educational and economic welfare: Nzolameso v Westminster CC [2015] UKSC 22, [2015] PTSR 549 para. 23.

It has been held that section 11 applies, not only to the formulation of general policies and practices, but also to their application in an individual case: Nzolameso v Westminster CC [2015] UKSC 22, [2015] PTSR 549.

Further, in ZH (Tanzania) v. SSHD [2011] 2 AC 166, per Baroness Hale at [25] and [26], it was held that in cases where human rights are engaged, the duty applied even to decisions which only indirectly affected children, such as where one or both parents are to live.

The Content of The Welfare Duty
The duty originated in the UN Convention on the Rights of the Child. Article 3(1) states that in all actions concerning children, whether undertaken by public or private social welfare institutions, courts of law, administrative authorities or legislative bodies, the best interests of the child shall be a primary consideration.

It is now clearly established that when Convention rights are engaged, section 11 has to be interpreted consistently with the UN Convention on the Rights of the Child: ZH (Tanzania) v Secretary of State for the Home Department [2011] 2 AC 166, H v Lord Advocate (Advocate General for Scotland intervening) [2013] 1 AC 413 and H (H) v Deputy Prosecutor of the Italian Republic, Genoa (Official Solicitor intervening) [2013] 1 AC 338. Those principles were summed up by the Supreme Court in Zoumbas v Secretary of State for the Home Department [2013] 1 W.L.R. 3690 as follows:

(1) The best interests of a child are an integral part of the proportionality assessment under article 8 of the Convention;
(2) in making that assessment, the best interests of a child must be a primary consideration, although not always the only primary consideration; and the child's best interests do not of themselves have the status of the paramount consideration;
(3) although the best interests of a child can be outweighed by the cumulative effect of other considerations, no other consideration can be treated as inherently more significant;
(4) while different judges might approach the question of the best interests of a child in different ways, it is important to ask oneself the right questions in an orderly manner in order to avoid the risk that the best interests of a child might be undervalued when other important considerations were in play;
(5) it is important to have a clear idea of a child's circumstances and of what is in a child's best interests before one asks oneself whether those interests are outweighed by the force of other considerations;
(6) to that end there is no substitute for a careful examination of all relevant factors when the interests of a child are involved in an article 8 assessment; and
(7) a child must not be blamed for matters for which he or she is not responsible, such as the conduct of a parent.

Decisions must be sufficient to show that the decision maker has discharged its duty under section 11: Nzolameso v Westminster CC [2015] UKSC 22, [2015] PTSR 549