In a new tactic to pressure Allina Health, striking nurses are seizing on an advocacy group’s report that says the hospital system lost millions of dollars borrowing in capital markets — wasting money that otherwise could improve pay, benefits and patient care.

At a news conference Wednesday, the Minnesota Nurses Association (MNA) highlighted the report, “Time to Pay the Piper,” produced by the Chicago-based ReFund America Project.

The report says Allina and other nonprofit organizations gambled and lost over the past two decades when they agreed to interest-rate “swaps” on bond issues arranged by Piper Jaffray, which left them paying reliable but high interest rates, while their banks paid variable rates that stayed at historic lows during and after the last recession.

MNA Executive Director Rose Roach said Allina’s losses on the financing strategy are “raising the cost of health care for every Allina patient and employee.”

The report estimates that Allina has lost $80 million on the bad interest-rate deals so far and that it could lose $175 million more before they are paid off.

Allina spokesman David Kanihan replied in a statement that “prudent” organizations use interest-rate swaps to protect against skyrocketing interest rates and that the union’s accusations benefit from the luxury of hindsight.

“The MNA’s contention is that Allina Health should have known in 1988 to maintain variable rate debt because there was a chance that interest rates would fall below 1.0 percent in 2016.”

Kanihan noted that Piper Jaffray was the underwriter, not the counterparty, in the rate swaps. He also criticized the union for using “a playbook of PR tactics” rather than seeking a solution to the strike.

Children’s Hospitals and Clinics of Minnesota, St. Olaf College and the city of St. Paul also are listed in the report as losing millions on the rate-swapping deals.

The report scrutinized Allina, because Piper Jaffray executives served on the health system’s board at the time of the deals, which have been profitable for their company.

As the strike nears its third week, nurses and union officials have been ramping up pressure on Allina board members. The MNA’s Roach on Wednesday called for the resignation of board member Debbra Schoneman, who is Piper Jaffray’s chief financial officer, and nurses conducted a brief demonstration in the lobby of the company’s Minneapolis headquarters.

The report was produced by Jordan Ash of the advocacy group Minnesotans for a Fair Economy in partnership with the ReFund project. Ash recommended that Allina at least try to renegotiate the deals to free up cash.