There’s trouble brewing in the world of home mortgages.

A report released last week by government regulators says that Fannie Mae has used improper accounting methods and challenges its financial reports.

Similar problems were identified last year at Freddie Mac, which was fined $125 million.

Freddie Mac and Fannie Mae finance about half the mortgages in the country. Their tentacles reach onto every street in America, including Wall Street. Fannie and Freddie package loans they have guaranteed and sell them to investors.

Federal Reserve Chairman Alan Greenspan has expressed serious concerns about the mortgage giants. He says that the two are so big, and involved in so many home loans, that their problems could threaten the country’s financial stability.

The two companies have been able to trade on the fact that they are government chartered, presenting themselves as a low-risk investment option. If either of the companies fail, a government bailout would be likely. For that, taxpayers and investors would pay dearly.

Congress has shirked its duties to regulate the companies, allowing oversight to slip. Experts suggest Freddie Mac and Fannie Mae control about $4 trillion in debt. That’s too big to ignore any longer. Stricter regulation is required. Otherwise, all our mortgage eggs could end up in two rickety baskets.