The government-sponsored enterprise (GSE) Fannie Mae ($0.00 0%) reported a serious delinquency rate for its mortgage portfolio of 5.29% in November 2009, the latest month of data, the highest in recent memory.

That number grew from 4.98% in October and more than doubled the 2.13% in November 2008, according to its monthly summary.

For December 2009, the entire Fannie book of business grew at an annualized rate of 9.7% in December to $3.2bn. For all of 2009, the book grew 4.2%.

Fannie’s mortgage-backed securities (MBS) and other guarantees totaled $2.82bn in December. It issued $55.3m in MBS - up from $40.3m in November – bringing its total issuance for the year to $807.8m.

Fannie’s gross mortgage portfolio grew at an annualized rate of 37.6% in December and stood at $772.5m at the end of the year.

Wilshire Credit Corp., the mortgage servicer bought by IBM ($192.42 -0.71%)  in October, is set receive a substantial servicing portfolio from Fannie and catch the servicing rights to a portion of these delinquencies. In fact, the mortgage finance industry is abuzz over a rumored change to the way Fannie and its brother GSE Freddie Mac ($0.00 0%) would assign and manage mortgage servicing rights.

Write to Jon Prior.