WASHINGTON - Lenders are ramping up efforts to avoid home foreclosures, but a report by bank regulators says more than half of borrowers who get help fall behind again.

More than 50 percent of homeowners with loans modified in the first half of last year had missed at least two months of payments a year later, the federal Office of the Comptroller of the Currency and the Office of Thrift Supervision said Wednesday.

The results were better among those who saw their payments drop substantially.

About 1 in 3 borrowers whose monthly payments were reduced by 20 percent or more had fallen behind again within a year. That compares with more than 60 percent for borrowers whose loan payments were left unchanged or increased.

The report highlights a significant challenge for the Obama administration's plan to tackle the foreclosure crisis, backed by $50 billion in money from the financial industry bailout fund.

The report covers 34 million loans, representing more than 60 percent of primary home mortgages. Consistent with other reports, it showed borrowers are continuing to fall behind as job losses mount. More than 11 percent of borrowers covered by the report had missed at least one payment as of June 30, up from 10 percent in April.

It also highlighted mounting problems with an especially troubling category of loans - "pick-a-payment" or option ARM loans, which allowed borrowers to defer some of their interest payments and add them to the principal. At the end of June, 10 percent of these loans were in foreclosure, more than triple the rate for all mortgages in the survey.

The lenders included in the report offered help to about 440,000 borrowers in the April-June period and started foreclosure on about 370,000 homes, unchanged from the January-March period.