(Reuters) - U.S. housing finance companies Fannie Mae and Freddie Mac could require more bailouts from U.S. taxpayers as risks are rising due to shrinking reserves, an internal watchdog for the firms' regulator said on Wednesday.

Washington bailed out the two firms in 2008 at the height of the financial crisis and has since seized all their quarterly profits while demanding the firms reduce their capital buffers.

"Future profitability is far from assured," Federal Housing Finance Agency Office of Inspector General said in a report, pointing out that the firms could again chalk up losses on their derivatives portfolios, similar to those they reported in the fourth quarter. 

"(This) increases the likelihood of additional Treasury investment," the report stated.

Fannie Mae's chief executive issued the same warning in February when the firm announced it would make its smallest payment to taxpayers in more than four years.

The possibility of another taxpayer draw raises pressure on the U.S. Congress to overhaul housing finance laws, although a real push on legislation is not expected anytime soon.

Taxpayers pumped $116.1 billion into Fannie Mae following the U.S. housing market collapse, while Freddie Mac was propped up with $71.3 billion. Both firms have already paid in dividends more than they received in aid.

The government-run companies do not lend money directly, but underpin the U.S. housing market by guaranteeing most new mortgages in the country.

Fannie Mae and Freddie Mac purchase loans from lenders and package them into securities that are then sold to investors.