Freddie Mac's portfolio swelled to a record $792 billion last month as the government-sponsored enterprise used its expanded buying powers to invest in securities it guaranteed.

The portfolio expanded at a 33% annual rate from a month earlier, the McLean, Va., GSE said in a volume summary Friday. Its mortgage assets rose at an annual rate of 53% in May and 42% in April after contractions in January and February.

Most of the $21.4 billion of growth last month came from $18.6 billion of net new purchases of mortgage-backed securities that Freddie helped to create and then guaranteed.

And the GSE plans to expand the portfolio further, according to the volume summary; its purchase commitments rose 32.4%, to $34.7 billion.

Regulators loosened their constraints on Freddie and Fannie Mae this year as part of an effort to pump money into the flagging mortgage market.

Fannie, which plans to release its June volume data this week, has used its new purchasing powers more conservatively, expanding its portfolio at an annual rate of 15% in May and 9.8% in April.

In addition to buying its own securities last month, Freddie also purchased $4.5 billion of mortgage bonds backed by Fannie or the Government National Mortgage Association and $920 million of new loans. Freddie cut its holdings of nonagency mortgage-backed securities by $2.6 billion.

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