Credit rating agencies have sought the intervention of their primary regulator, Sebi, in the wake of new directions from the Reserve Bank of India (RBI) and the contradictions that have surfaced in the views of the two financial market watchdogs. The central bank has said ratings given on loans to a company cannot be notched up on the basis of "diluted and non-prudent support structures" such as letter of comfort, letter of support or undertaking, and other covers like pledge of shares. Such support from the parent or promoters enables companies to reduce the cost of borrowings - as higher the rating, lower the interest charge on debt. Even for apparently more enforceable support such as corporate guarantees (as distinct from letter of comfort), RBI said such structures can be used to enhance rating only if there is a strict timeline on invocation of guarantee by lenders.