The state's Medicaid office improperly paid over $15 million in taxpayer dollars for programs that aid disabled adults, according to a report being issued by State Auditor Suzanne Bump Thursday.

Bump's investigators concluded that between 2010 and 2015, MassHealth, the state agency that distributes federal Medicaid services in Massachusetts, paid out $15,201,854 for duplicate adult foster health care services for patients already in long-term care facilities that provide similar services.

"So essentially, the state was paying twice," Bump told WGBH News.

MassHealth serves almost 2 million lower-income Massachusetts residents with disabilities, according to the report. The agency paid out $1.3 billion for adult foster care for over 6 million claims from 2010 to 2015.

MassHealth offers eligible elderly and disabled members assistance in performing daily activities like dressing, eating, using the bathroom and walking, through the adult foster-care programs. Services are also made available for less crucial tasks like laundry, shopping, meal preparation, medication management and cleaning. Recipients live in the private residences of caregivers contracted with MassHealth.

"Both programs are designed to provide sufficient assistance to allow members to continue to live independently and avoid the high cost of a long-term care (LTC) facility," the report reads.

Bump said she doesn't think the problems with adult foster care payment have anything to do with the change from a Democratic administration in the corner office to a Republican one.

"In fact, I would have thought that this administration would have been even quicker on the uptake because they are extremely focused on management changes to control costs, and yet they let this one lapse," she said.

MassHealth disagrees with Bump's findings. The agency claims that rest homes for the elderly, one of several categories of long-term facility analysed by Bump and her team, are not covered by Medicaid and therefore patients residing in them are eligible for additional state care.

"While they provide protective housing environments for the elderly, they do not provide the same level of medically necessary assistance ... that is provided under the [group adult foster care] program," MassHealth responded to Bump.

The audit claims MassHealth was paying providers to care for clients already receiving similar services in long-term facilities.

"These were the same services being provided by staff members at the LTC facilities who are responsible for assisting members throughout the day," the audit says. "The AFC and GAFC programs are designed to provide members with sufficient daily assistance to avoid placement in LTC facilities, not to supplement services in those facilities."

MassHealth's own regulations, the audit claims, "state that MassHealth does not pay for [adult foster care] or [group adults foster care] services provided to members residing in long-term-care (LTC) facilities."

Bump disagrees with MassHealth's assessment that rest homes are covered under adult foster-care regulations.

"Our audit work showed that rest-home services and GAFC services were essentially identical and resulted in duplicative payments of more than $15 million by the Commonwealth," she wrote in response.

In 2013, MassHealth issued a letter to their contracted adult foster-care providers saying that despite those regulations, they would continue to pay for group foster-care services for patients already receiving them and living in long-term facilities.

Bump said the most disturbing thing in the audit is MassHealth's response, which she described as denying there was anything wrong with them paying for adult services for patients already in rest homes when their own guidance states that the practice is not allowed.

"They themselves saw that they were paying for services to individuals who were in rest homes," Bump said. "They themselves determined that this was inappropriate."

Bump's audit comes down hard on MassHealth for violating its own guidelines and not addressing how to fix the problem.

However, almost three years later, MassHealth has still not enacted these new regulations or implemented claim-processing system edits that would prevent payment for [adult foster care] and [group adult foster care] services for members in [long term care] facilities.

Bump's report suggests MassHealth should set up systems to detect and deny payment claims for adult care services for patients already being cared for in long-term facilities.

In all, MassHealth pays health care providers more than $13 billion annually, half coming from state revenues, representing over one-third of the state's budget spending.

The auditor's office looked into MassHealth's payments for adult foster care after Bump's Bureau of Special Investigations identified potential "weaknesses in MassHealth’s claim-processing system," according to the report.

Bump stressed the the audit found no fraud or wrongdoing by recipients of the care or providers.

"They determined that the recipients were not at fault here, it's MassHealth program administration that is at fault here," she said.

Bump said the team was initially investigating possible fraud by the recipients of the care while in rest homes when they found it was MassHealth policies that allowed it to happen. Bump says what seems to be happening is that MassHealth services are being used to supplement the staffs of the rest homes where the improper services are happened.