The Court of Appeal delivered a judgment in Re B (A Child)  EWCA Civ 1579 last month. In it they consider (but do not resolve) the question of how the Family Court should deal with evidence obtained by covert recording.
Implication is that covert recordings of both children and adults are admissible in the family courts, but the weight of consideration given to such evidence remains a subjective determination for judges.
The Family Justice Council has been invited to produce guidance on this topic.
Leeds LSCB have produced helpful practice guidance (2017) ‘Recording of meetings and conferences by parents’.
Transparency project guidance document (2018) ‘Parents recording social workers - A guidance note for parents and professionals’