U.S. foreclosure rates are up against more than stubborn banks, as homeowners also choose to abandon their mortgages, economists said.

Credit score company Experian and consultants Oliver Wyman reported 588,000 borrowers voluntarily gave up on their mortgage payments in 2008, twice as many as the previous year, USA Today reported Tuesday.

With home prices low, many find their homes financially underwater, meaning they owe more on their mortgages than the home is worth. Under those conditions, the futility of making payments, especially if a breadwinner has lost a job, cause many to walk away and let the bank take the home.

"It's increasingly a more important factor driving the foreclosure crisis," said economist Mark Zandi at Economy.com.

Home prices are down more than 50 percent from their peak in Las Vegas and Phoenix and about 25 percent below on a national scale.

CitiMortgage, part of Citigroup, said 20 percent of their defaults are the result of homeowners strategically giving up on their loans.

"It's a very large number and it's a very, very significant risk to the housing recovery," said Sanjiv Das, chief executive officer of CitiMortgage.