WASHINGTON – Congress is yet again asking New York-Presbyterian Hospital to provide detailed information about its operations. This time, a House panel is scrutinizing how the nation’s largest hospitals bill their uninsured patients and people injured in automobile accidents.

The inquiry comes as Capitol Hill lawmakers are becoming increasingly concerned that hospitals are accepting public funds and tax breaks to provide care to the poor and uninsured while driving many such patients into bankruptcy through inflated charges and aggressive bill collection.

“Hospitals often expect uninsured/ self-pay patients to pay far more for their care than what the hospitals would otherwise accept from managed care or government programs, and then sometimes aggressively pursue these patients for this debt,” the chairman of the House Committee on Energy and Commerce, Rep. Joe Barton, a Republican of Texas, wrote in a recent letter to New York-Presbyterian and a handful of the nation’s largest hospitals.

Uninsured patients across the country are often charged prices that are two to four times what the procedures cost the hospital and are several times greater than the charges paid by insurance companies or Medicare for the same procedures, a professor of public health at Johns Hopkins School of Medicine, Dr. Gerard Anderson, told Mr. Barton’s committee at a hearing last June.

The committee is also asking whether and how the hospitals actually communicate to patients that they are entitled to reduced bills, thanks in part to public subsidies and tax breaks given to the hospitals to offset the costs of charitable care.

In a recent nationwide survey, a patient advocacy group, the Access Project, found that most hospitals are reluctant to give out details about their charitable care policies, partially out of concern that patients could “game the system” if they knew the income cut-off levels that would qualify them for discounted care.

“Our experience in general is that often people seem to qualify for existing programs, but aren’t informed of them, and are billed and dunned and have these medical debts lingering for many years,” the group’s executive director, Mark Rukovina, who has also testified before the panel, said.

The committee is also probing higher charges for so-called out-of-network patients, who have insurance but by chance or circumstance find themselves using a hospital that has not negotiated discounted rates with their insurer, as well as people treated for injuries caused by auto accidents who have little control over where they are treated.

The panel is also reviewing the clarity of bills sent to uninsured patients.

“Health care consumers must be given every opportunity to understand exactly what they are paying for and how much they are paying,” Mr. Barton wrote, noting that uninsured patients are in greatest need of clear information.

A spokeswoman for the New York-Presbyterian, Myrna Manners, said the hospital had not yet formulated a reply to the letter, and she declined to comment on it.

A spokesman for Mr. Barton’s committee, Kevin Schweers, said New York-Presbyterian was not singled out because of concerns about its practices, but because it is one of the nation’s biggest urban hospitals. It is too early to say whether the committee’s questions will lead to federal legislation, he said.

Mr. Barton’s inquiry comes in tandem with two other investigations affecting New York-Presbyterian, the city’s largest hospital and biggest private-sector employer.

The chairman of the Senate Finance Committee, Senator Grassley of Iowa, asked the hospital to give detailed information about its finances and compensation of executives as part of an investigation into the tax-exempt status of nonprofit hospitals.

The House Ways and Means Committee has also been holding hearings examining whether not-for-profit hospitals are providing sufficient public interest and charitable service to justify lucrative tax exemptions.

Committee members are discussing possible legislation to set out clearer charity care requirements for hospitals that enjoy federal tax exemptions.

The president and CEO of New York-Presbyterian, Herbert Pardes, testified to Mr. Barton’s committee last June that the hospital goes out of its way to assist uninsured patients.

The hospital provides nearly $70 million in charity care each year, and it writes off an additional $70 million in bad debt resulting from the unpaid balances of self-pay patients, he said.

The hospital provides charity care/financial aid for patients with incomes up to 300% of the federal poverty level, or $56,550 for a family of four. In addition, it routinely assesses patients’ eligibility for assistance from the Philanthropic Fund, which is used to pay the medical bills of patients experiencing financial hardship. For ineligible patients, the hospital establishes flexible payment arrangements based on the patient’s individual circumstances, he said.

On average, the hospital collects only 12% to 13% of the charges for services to self-pay patients, he said.

But advocates for patients in New York City say that despite such stated policies, many of the city’s uninsured patients continue to be turned away, are forced to pay-up front for services, or are charged at rates several times as high as insured patients.

“New York-Presbyterian claims that they have all these great charity care policies,” said a former legal aid lawyer who worked with patients struggling to pay hospital debts, Elizabeth Benjamin, who said she has had an uninsured client denied treatment there. “It doesn’t seem to have trickled down to the frontline staff.”

The state hands out $849 million to hospitals each year to offset the costs of charitable care and bad debt through the Bad Debt and Charity Care Pool.

But there is no requirement in New York law that the state funds go directly to the patients, or that the hospitals actually provide charitable care.

It is common practice for hospitals to hire collection agencies to pursue the patients, down to garnishing wages, taking liens against homes, and writing off the costs of charitable care or bad debt only once all options are exhausted. By then, the often-ailing patient’s credit can be ruined with little financial gain for the hospital.

“We are supposed to take it on good faith that they are using this money to help low-income people or people without heath insurance. It’s quite a shocking thing,” said Ms. Benjamin, now with the New York Civil Liberties Union. The state ought to legislate clear standards for all hospitals receiving subsidies, she said.

There are an estimated 1.8 million uninsured city residents, nearly one out of four New Yorkers.

In March, the U.S. District Court for the Southern District of New York dismissed a lawsuit claiming that New York-Presbyterian Hospital, as a tax-exempt charitable institution, was required by federal and New York law to provide hospital care to uninsured patients at rates no higher than those it had negotiated with health-insurance carriers or paid by government programs. The district court held that none of the plaintiffs’ claims had any basis in federal or New York law, and that the issues should instead be addressed through the political process.