Washington - The United States launched a new crackdown Monday on mortgage fraud that may have contributed to the country's worst housing downturn in decades.

The US Justice Department, Treasury and other government agencies announced a joint effort to target bogus companies that have sprouted up offering mortgage refinancing and foreclosure help.

More than 3 million people were in foreclosure in 2008, a record that helped drive down US home prices and spurred the financial crisis that has plunged the world into recession.

Most of the foreclosures came from holders of sub-prime mortgages - loans to borrowers with poor credit that start with a low borrowing rate that can rise sharply after a time. Lawmakers have criticized mortgage lenders for misleading borrowers about the terms of their loans.

Treasury Secretary Timothy Geithner said the new nationwide crackdown was aimed at preventing criminals from preying on struggling homeowners as the administration takes steps to help people keep their properties.

"Just as this administration intensifies our efforts to help American homeowners, those who would seek to prey on the most vulnerable are intensifying their tactics as well," Geithner said. "These predatory scams callously rob Americans of their savings and potentially their homes."

The new measures are designed to detect scams earlier and include working with the financial sector to help them identify the signs of fraudulent companies.

"For millions of Americans, the dream of home ownership has become a nightmare because of the unscrupulous actions of individuals and companies who exploit the misfortune of others," said Attorney General Eric Holder.