1. An institution may decide to nominate one or more ECAIs the credit assessments of which shall be used in the calculation of its risk-weighted exposure amounts under this Chapter (a ‘nominated ECAI’).
2. An institution shall use the credit assessments of its securitisation positions in a consistent and non-selective manner and, for these purposes, shall comply with the following requirements:
(a) an institution shall not use an ECAI’s credit assessments for its positions in some tranches and another ECAI’s credit assessments for its positions in other tranches within the same securitisation that may or may not be rated by the first ECAI;
(b) where a position has two credit assessments by nominated ECAIs, the institution shall use the less favourable credit assessment;
(c) where a position has three or more credit assessments by nominated ECAIs, the two most favourable credit assessments shall be used. Where the two most favourable assessments are different, the less favourable of the two shall be used;
(d) an institution shall not actively solicit the withdrawal of less favourable ratings.
3. Where the exposures underlying a securitisation benefit from full or partial eligible credit protection in accordance with Chapter 4, and the effect of such protection has been reflected in the credit assessment of a securitisation position by a nominated ECAI, the institution shall use the risk weight associated with that credit assessment. Where the credit protection referred to in this paragraph is not eligible under Chapter 4, the credit assessment shall not be recognised and the securitisation position shall be treated as unrated.
4. Where a securitisation position benefits from eligible credit protection in accordance with Chapter 4 and the effect of such protection has been reflected in its credit assessment by a nominated ECAI, the institution shall treat the securitisation position as if it were unrated and calculate the risk-weighted exposure amounts in accordance with Chapter 4.