WASHINGTON — Senator Schumer called on Countrywide Financial Corp. to waive prepayment penalties, refinance loans, and eliminate “above-market fees” to help homeowners struggling to make payments on subprime mortgages.

Countrywide, the biggest American mortgage lender, should stop paying higher commissions to brokers who steer borrowers to high-cost loans that “are designed to fail,” Mr. Schumer told reporters in Washington yesterday.

“I am calling on Countrywide, as our nation’s largest lender, to bury its bad business practices and reverse some of the damage it has already inflicted on our housing market,” Mr. Schumer said.

Mr. Schumer, a member of the Senate Banking Committee, has been among the most vocal lawmakers seeking tighter restrictions on mortgage brokers. He introduced legislation in May to set America standards for brokers, including requiring them to assess a borrower’s ability to repay at a loan’s highest interest rate.

“Countrywide’s most lucrative brokers are those that make bad loans that are largely designed to fail the borrower,” Mr. Schumer said. The company’s brokers can earn an extra 1% of the loan value in commission by adding a three-year prepayment penalty to loans, the senator said.

The Calabasas, Calif.-based lender got a $2 billion infusion of capital last week from Bank of America Corp. to allow it to keep funding loans after being shut out of short- term debt markets. At least 90 American mortgage companies have halted operations or sought buyers since the start of 2006, according to Bloomberg data.

Mr. Schumer cited an August 26 New York Times article that featured interviews with former Countrywide employees who said potential borrowers were promised “the best loan possible” and then steered into high-cost and sometimes unfavorable loans that resulted in higher commissions for the company’s sales force.

Senator Obama, a Democrat from Illinois, who is seeking his party’s presidential nomination, also called for reining in “unlicensed, unregulated, fly-by-night” mortgage brokers in a column in yesterday’s Financial Times.

In recent months, Democrats in Congress have amplified their concerns about the soaring rate of foreclosures among subprime borrowers, those with weak credit or high debt. Senator Clinton said this month she planned to introduce legislation that would ban penalties for people who pay off mortgages early and require federal registration of mortgage brokers.

The chairman of the Senate Banking Committee, Senator Dodd, and the chairman of the House Financial Services Committee, Barney Frank, a Massachusetts Democrat, have used hearings to prod regulators to write new rules restricting deceptive lending practices.

Countrywide didn’t immediately respond to a request for comment.