New York ? The mortgage crisis is spreading and hitting new heights: Borrowers with good credit now make up the largest share of foreclosures as job losses and pay cuts exact their toll.

A record 12 percent of homeowners with a mortgage were behind on their payments in the first quarter, the Mortgage Bankers Association said Thursday. The trend is predicted to continue until the end of next year, about six months after unemployment is expected to peak.

The genesis of the recession — risky adjustable-rate loans made to borrowers with bad credit — remains a significant factor in foreclosures. Today, almost half of all subprime ARMs are past due or in foreclosure.

When those borrowers started defaulting in droves in late 2006, it forced dozens of lenders out of business and sparked a credit crisis in the summer of 2007. Businesses nationwide couldn’t get short-term loans to finance new orders or even cover their payrolls.

The impact has now filtered out, consuming homeowners who until recently had a good track record of paying their bills on time. Nearly 6 percent of these prime borrowers with fixed-rate mortgages were past due or in foreclosure, nearly doubling in the last year.

The worst of the trouble continues to be focused in California, Nevada, Arizona and Florida, which accounted for 46 percent of new foreclosures nationwide and reported the worst delinquency and foreclosure rates on prime fixed-rate loans. The four have suffered massive job cuts in the housing industry. There were no signs of improvement.

But experts expect the pain to spread throughout the country as job losses mount. MBA’s chief economist Jay Brinkmann estimates the unemployment rate will top out in mid-2010 and foreclosures to abate about six months afterward.