A re-think on the risks of credit losses by the funders of Australia's A$1.3 billion home loan pool has led to a cut in the ratings of three lenders' mortgage insurance companies by Moody's Investors Service.Moody's has downgraded the insurance financial strength ratings of:- Genworth Financial Mortgage Insurance Pty Ltd to A3, from A1- Genworth Financial Mortgage Indemnity Ltd, an associated company, from A3 to A2- QBE Lenders' Mortgage Insurance Limited to A2, from Aa3.Moody's maintained its rating on Westpac Lenders Mortgage Insurance at Aa3.Nine months ago, Moody's said it had the ratings of Australia's mortgage insurance sector under review.All the new ratings carry a stable outlook.Moody's said it "does not expect these rating actions on the mortgage insurers to affect its ratings of Australian banks and building societies."It said that "the mortgage loan books of the banks have low average loan-to-value ratios and a small percentage of riskier, non-standard loan products, such as low documentation loans."Moody's did note, however, that "the modelling does indicate the potential for elevated losses in some regions, which will continue to inform ratings assigned to local financial institutions."Moody's said it was still assessing the impact of the revised LMI ratings on Australian mortgage-backed securities that benefit from LMI policies.