Most U.S. hospitals are not complying with federal regulations requiring medical centers to post their prices online for patients to review, according to a new report by patient advocates.

The report, which surveyed the websites of 500 of the roughly 6,000 hospitals subject to the rule, found that 471 of the hospitals did not fully post the prices they charge patients and the rates they have negotiated with insurers. The federal price transparency rules took effect Jan. 1.

Hospitals’ failure to post prices is complicating patients’ ability to shop for care, said Cynthia Fisher, the founder of Patient Rights Advocate, which conducted the report and submitted a copy to the White House on Thursday. The nonprofit group said it believes its survey of transparency measures is representative of hospitals overall.

“Right now, we see these hospitals being anti-competitive and not posting their prices, including the prices that they’ve negotiated with insurers,” Fisher said. “We’ve seen wide price variation within the same hospital for the same services.”

The report comes one week after President Biden instructed his health department to enforce the hospital price transparency rules, which were crafted by the Trump administration. Hospitals that do not comply can face a penalty of up to $300 a day, which advocates say is insufficient to compel the industry — which has spent years fighting price transparency efforts and sued to block the rules — to post prices that hospitals have negotiated with insurance companies.

“We think that President Biden can continue to hold them accountable by enforcing stricter, higher and more meaningful penalties,” Fisher said.

The report faulted a number of hospitals in the D.C. region for not complying with all or part of the federal regulations.

For instance, the report said MedStar Georgetown University Hospital, MedStar National Rehabilitation Hospital and MedStar Washington Hospital Center did not comply with a requirement to post the cash prices that patients would pay. The hospitals’ price transparency disclosure forms instead say MedStar “does not have a standard cash price. The amount is determined based on patient-specific circumstances.”

MedStar spokesman Brendan McNamara said the system could not comment on the report’s findings until after a review.

“MedStar Health is committed to enhancing price transparency and is meeting federal requirements at all of our hospitals,” McNamara said.

BridgePoint Healthcare — a privately run system with facilities on Capitol Hill and near National Harbor — publicly posted what is known as a “charge master,” a technical list of items that are billed to insurers. But it did not post the more comprehensive list of prices for patients to navigate, Patient Rights Advocate said.

BridgePoint did not immediately respond to a request for comment.

Elected officials have pushed for greater health-care price transparency, although experts have cautioned that the policy’s effects may be limited.

In a December 2020 survey, the Kaiser Family Foundation found that 96 percent of Democrats and 91 percent of Republicans supported “making information about the price of doctors’ visits, tests, and procedures more available to patients.” But a follow-up Kaiser Family Foundation poll in May found that just 9 percent of adults were aware hospitals were required to post the information online, and only 14 percent said they or a family member had gone online to research the cost of hospital care in the past six months.

“This is a very popular policy position, but it’s not something a lot of people at the moment are taking advantage of — or even know about,” said Mollyann Brodie, a Kaiser Family Foundation executive vice president who oversees the organization’s polling.

Some former Trump officials and advisers praised Biden’s call last week to enforce the price transparency rules.

“I couldn’t be more pleased” with Biden’s move, said economist and Trump adviser Arthur Laffer, appearing on a Fox Business show hosted by Larry Kudlow, who led the National Economic Council during the Trump administration.

“When the Dems do something good, we praise them,” Kudlow responded.

Brian Blase, a policy consultant who served as a special assistant to Trump and helped craft the last administration’s price transparency rules, credited the “positive signs” from the Biden administration but said the White House needed to demonstrate that it would actually impose the rules.

“It’s hard to know whether they are going to devote resources toward successful implementation or just talk about how they support transparency but not make it a priority,” Blase said.