Healthcare advocates caution a merger between two Greater Boston hospital networks would send costs sky-high.

The merger of Beth Israel Deaconess Medical Center and Lahey Health could increase medical spending by as much as $191M annually, according to a preliminary report released Wednesday by the Massachusetts Health Policy Commission. Critics of the proposed union viewed the report as a worst-case scenario, the Boston Herald reports.

“This report confirms our worst fears, that the merger will leave communities of color behind in order to generate bigger profits,” Hanoi Reyes, a spokesperson for healthcare watchdog the Make Healthcare Affordable Coalition, told the Herald.

The HPC report forecast the merger would call for as much as $51M in additional inpatient care costs, between $88M and $128M in outpatient costs and $12M for primary care physicians.

The Beth Israel-Lahey merger would involve 13 hospitals and be one of the largest Massachusetts healthcare deals in decades, but news of its cost impact comes amid a greater push to bring costs down.

Amazon, Berkshire Hathaway and JPMorgan Chase selected Boston last month as the headquarters city for a co-venture to bring affordable healthcare options to employees.

Massachusetts Attorney General Maura Healey has already indicated her concern with the higher costs associated with the Beth Israel-Lahey merger, and the report adds pressure for her to act on the deal. A spokesperson for Healey said she was reviewing the 138-page report and expects to speak to officials with both organizations within days.