Freddie Mac reported an $821 million loss in the second quarter, the fourth consecutive quarterly loss for the mortgage giant. At the same time, it announced plans to cut its common stock dividend and warned that the tough times are not over.

The company’s second quarter loss follows a $151 million loss in the first quarter and compares with a profit of $729 million a year earlier. Losses for the past four quarters totaled over $4.6 billion.

Freddie said it expects to reduce the dividend on its common stock in the third quarter from $0.25 to $0.05 or less per share and to pay the full dividends at contractual rates on its preferred stock, subject to approval by its board of directors.

Estimated regulatory core capital was $37.1 billion as of June 30, 2008, an estimated $8.4 billion more than its statutory minimum capital requirement and $2.7 billion above the 20 percent mandatory target capital surplus, the earnings announcement said. However, the company also noted that the market conditions that drove its share price down “are likely to affect our approach to raising new core capital including the timing, amount, type and mix of securities we may issue.”

Freddie Mac and Fannie Mae were propped up by Congress last month as part of the housing bill after its stock tumbled in response to rumors it would not have sufficient capital to offset huge losses from delinquent mortgages.

Second quarter provision for credit losses more than doubled as a result of rising delinquencies, foreclosures, and estimated losses from falling home prices, rising to $2.5 billion in the second quarter from $1.2 billion in the first quarter.

Security impairments on available-for-sale securities were $1.0 billion for the quarter, Freddie Mac reported. These were largely related to securities backed by subprime or Alt-A and other mortgages.