WASHINGTON — The number of homeowners dropping out of the Obama administration's main mortgage assistance plan is growing, and is now almost equal to the number who have received permanent relief.

The Treasury Department's report yesterday was the latest evidence of problems in the administration's $75 billion program. While officials insist the program is helping the housing market turn around, critics say it is merely delaying an inevitable surge in foreclosures.

More than 299,000 homeowners had received permanent loan modifications as of last month, Treasury said — about 25 percent of the 1.2 million who started the program since it began in March 2009. On average, they pay $516 less each month.

However, the number of people who started the process but failed to get their mortgages permanently modified rose dramatically in April.

To complete the program, borrowers must make at least three payments on time. About 277,000 homeowners, or 23 percent of those enrolled, have dropped out during this trial phase. That's up from about 155,000 a month earlier, or a 79 percent increase.

Many borrowers are still stuck in limbo, unable to complete the process and caught up in an often-bewildering bureaucracy.

"These mortgage companies have to get it together," said Henrietta Thompson, housing coordinator with United Family Services in Charlotte, N.C. "We're not getting anything done."

Treasury officials acknowledge long delays have been a problem. "Homeowners are waiting. We want them to get answers as rapidly as possible," said Herbert Allison, an assistant Treasury secretary.

The program is designed to lower borrowers' monthly payments by reducing mortgage rates to as low as 2 percent for five years and extending loan terms to as long as 40 years. Mortgage companies, also known as loan servicers, get up taxpayer incentives to reduce borrowers' monthly payments.

But there have been problems from the start. One of the big ones: Initially, many of the participating banks allowed borrowers to state their income verbally and provide proof of their income later. That jammed up the system as many borrowers didn't provide a complete set of documents, and some complained that their information was lost.

Starting with loan modifications that go into effect June 1, lenders will be required to collect two recent pay stubs at the start of the process.

Many borrowers who don't get help will end up losing their homes. That can happen through foreclosure. Another option is a short sale, which is when banks agree to let borrowers sell their homes for a reduced price if they owe more than it's worth.

To encourage more of those sales, the Obama administration is giving $3,000 for moving expenses to homeowners who complete such a sale or turn over the deed of the property to the lender.