Oversight mechanisms Effective complaints procedures are a basic safeguard against ill-treatment in detention but complaint mechanisms are useless if the persons concerned do not know about them. FRA opinion 8 When designing approaches to immigration detention of children, EU Member State authorities should make full use of the advice and engage the participation of ombuds institutions and National Human Rights Institutions, especially those with child-specific mandates. Child protection authorities in EU Member States should devote primary attention to children deprived of liberty for immigration purposes. Responsible authorities should consult child protection agencies, at least when assessing whether or not to detain a  child together with their parents. Child protection authorities should also regularly visit children held in immigration detention. The European Commission could consider undertaking unannounced Schengen evaluation visits if there is evidence of arbitrary use of child detention pending removal in a given EU Member State. EU  Member States should ensure that each detention or other holding facility offers childaccessible ways to submit complaints, for example through a complaint box, and that they inform children in a child-friendly manner about their right to lodge a  complaint. Responsible authorities should follow up on each individual complaint. 95