Fannie Mae's gross mortgage portfolio shrank sharply in November while the delinquency rate on single-family loans it guarantees leaped in October, the government-controlled U.S. home funding company said on Monday.

The company said its mortgage investments fell at a 26.1 percent annual rate last month to $752.2 billion. Year-to-date, the portfolio has declined by an annual 4.9 percent from $787.3 billion at the end of last December.

Fannie Mae also reported an ongoing jump in the rate of late payments on single-family loans it guarantees, a problem that has eaten into its capital and forced borrowing from the U.S. Treasury.

In October, the most recent figures available, the conventional single-family serious delinquency rate rose 26 basis points to 4.98 percent. A year earlier, the rate was 1.89 percent.

The multifamily serious delinquency rate dipped 1 basis point to 0.61 percent but remained starkly higher than the 0.21 percent rate in October 2008.

Loans that are three months or more past due or in the foreclosure process for single-family homes and those that are 60 days or more past due for multifamily homes are considered serious delinquencies.

The mortgage holdings of Fannie Mae and Freddie Mac, the second-largest U.S. home funding company, which is also government-controlled, have long been at the heart of political debate about risks taken by these massive housing entities.

The portfolios of both companies were to have been trimmed by 10 percent annually from their balances as of the end of December. But on Thursday the Treasury amended that decision. The downsizing will now take place from a cap of $900 billion rather than the year-end sizes.

Freddie Mac's mortgage portfolio declined in November at a 2.2 percent annual rate to $761.8 billion.

Fannie mae Mortgage Freddie mac