At the time of application for foster care, or as soon as practicable thereafter, the appropriate social services official must determine the appropriateness of making a referral to the child support enforcement unit of the social services district. The assessment of appropriateness for such referral must be made separately for and must distinguish between the former custodial parent and the non-custodial parent. Such determination must be made in accordance with the criteria set forth in section 422.4(b) of this Part.