New mortgage delinquencies reported by Radian Guaranty Inc., the mortgage insurance subsidiary of Radian Group Inc., rose 8.6 percent in May and the major mortgage insurer reported a slower pace of the decline in its delinquency inventory.

Radian reported 7,844 new delinquent mortgages in May, compared to 7,222 in April. However its net delinquent inventory for the month was 114,193 primary loans, compared to 115,020 in April.

Radian’s increase in delinquencies reflects a national uptick in delinquencies during the first quarter reported last month by the Mortgage Bankers Association.

According to the MBA, the delinquency rate for mortgage loans increased to a seasonally adjusted rate of 8.32 percent of all loans outstanding as of the end of the first quarter of 2011, an increase of seven basis points from the fourth quarter of 2010, and a decrease of 174 basis points from one year ago, according to the Mortgage Bankers Association’s (MBA) National Delinquency Survey. The non-seasonally adjusted delinquency rate decreased 117 basis points to 7.79 percent this quarter from 8.96 percent last quarter.

However, the serious delinquency rate, the percentage of loans that are 90 days or more past due or in the process of foreclosure, was 8.10 percent, a decrease of 50 basis points from last quarter, and a decrease of 144 basis points from the first quarter of last year.

Last month Jay Brinkmann, MBA’s chief economist, said, “Most of these numbers continue to point to a mortgage market on the mend. Short-term delinquencies remain at pre-recession levels. Loans 90 days or more delinquent have now dropped for five straight quarters and are at their lowest level since the beginning of 2009. Foreclosure starts are at the lowest level since the end of 2008 and had the second largest drop ever. The percentage of loans somewhere in foreclosure is down from last quarter’s record high and also had one of the largest drops we have ever seen, although the reasons for the drop will differ from market to market.”

“Of particular importance is that the drop in the percentage of loans 90 days or more past due was driven by improving numbers for loans originated between 2005 and 2007. These are the loans that drove the mortgage market collapse and now represent about 31 percent of loans outstanding but 65 percent of the loans seriously delinquent. Given that loans originated during this period are now past the point where loans normally default, and that loans originated since then generally have better credit quality, mortgage performance should continue to improve,” Brinkmann said.

Radian Guaranty provides credit protection for mortgage lenders and other financial services companies on home assets through traditional mortgage insurance as well as other mortgage-backed structured products. The company provides primary and pool private mortgage insurance on residential first-lien mortgages. (Private mortgage insurance is generally required when a loan amount exceeds 80% of the property’s value) Its customers include some 3,500 residential lenders in the US. Primary insurance on first-lien mortgages accounts for 90% of Radian Guaranty’s sales and accounts for more than half of its parent’s revenues.