Freddie Mac's portfolio of mortgage assets grew at an annual rate of 66% last month, its fastest pace ever, as regulators pushed the government-sponsored enterprise to ease constraints on the U.S. housing market.

The portfolio rose by $41.7 billion in November, to an all-time high of $805.4 billion, Freddie said last week in its monthly volume summary. The percentage increase was the largest on record, according to Kathryn Courbe, a spokeswoman for the McLean, Va., company.

Purchases by Freddie and the larger Fannie Mae are part of a government effort to bring down mortgage rates to curb a housing slump that has been at the center of a yearlong economic recession.

The Treasury Department bought $49.7 billion of their home loan securities in September, October, and November, and the Federal Reserve Board last month announced plans to purchase as much as $500 billion of mortgage bonds.

The share of mortgages at least 90 days late among single-family loans that Freddie either owns or guarantees within bonds rose to 1.52% in November, the company said. The rate was up from 0.60% a year earlier and 1.34% in July.

Freddie and Fannie, which slowed their growth to protect against rising delinquencies, were seized by regulators on Sept. 6 and directed to focus on helping struggling homeowners.

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