Attorneys general in six states have filed suit against GMAC Mortgage Corp., accusing the lender of overcharging consumers by millions of dollars in escrow payments.

The action seeks to bar the Detroit-based lender from building big cushions into escrow accounts and to force GMAC to recalculate the way it determines escrow payments. GMAC holds about 400,000 mortgages nationwide.

Attorneys general from California, Iowa, Massachusetts, Minnesota, New York and Texas filed suit Tuesday in federal court in Manhattan.

The six states acted because the federal government has not enforced its own laws against the practice, New York State Attorney General Robert Abrams said.

Abrams said that if the suit succeeds, homeowners could receive millions of dollars in refunds.

Officials from GMAC Mortgage, a subsidiary of General Motors Corp., declined to comment on the suit.

In April, the attorneys general released a study critical of mortgage lenders' practice of requiring excess funds in escrow accounts.

"When we released the report of the illegal escrow practices of GMAC and other lenders, we urged the federal government to enforce its own statutory limits on escrow payments. So far, it has taken no action, thus prompting suits like {this one} at great cost to the states," Abrams said.

That study said consumers were being overcharged $2 billion to $4 billion by the nation's mortgage lenders.

Lenders maintain escrow accounts to make payments for property taxes, insurance and other items that borrowers must pay. Extra money in escrow accounts hurts consumers but is a bonanza for lenders, who regulators say get to use the funds for free or by paying a very low rate of interest on them.

About two-thirds of the nation's home mortgages involve escrow accounts.

Federal law limits lenders to keeping a two-month "cushion" in escrow, or enough money to make payments for two months. The cushion allows lenders to make tax and insurance payments even if the consumer is late making a monthly payment.

"Our report estimated that the 'excess cushion' averages about $150 per homeowner," Iowa Attorney General Tom Miller said. "That means we think lenders are holding several billion dollars that should be in the hands of their customers."

The report called on Housing and Urban Development Secretary Jack Kemp to tighten enforcement of the law. The attorneys general said inaction by HUD led them to file the suit.

The two-year study focused on big lenders who operate nationwide. A survey of four of the largest -- Citibank, GMAC Mortgage Corp., Fleet Mortgage Corp. and Lomas Financial Group -- "indicated that lenders may be holding excessive and illegal cushions in more than 70 percent of escrow accounts."