An attorney for the Medford fire union is accusing Mayor Breanna Lungo-Koehn of breaking the law by offering a firefighter from outside the city to serve as interim chief, but the mayor says she’s in the right as she followed the city charter.

The Medford Fire Department has been operating without a chief since John Freedman retired Wednesday after nearly 30 years of service, serving as the department’s leader in the final two.

Uncertainty is growing around whether the next chief will be hired from within the department as Lungo-Koehn is pushing for the city’s removal from civil service law which requires promotions be made internally only.

Lungo-Koehn brought to light how a candidate from outside the department declined an offer she made him to act as interim chief due to potential negative pushback during a heated City Council discussion on her proposal last week.

The council sent the mayor’s request to a committee for further discussion.

Medford has been divided since a wave of sick callouts within the fire department earlier this month cost the city nearly $100,000, Lungo-Koehn alleges. The mayor has described the situation as an “orchestrated event.”

Freedman announced his retirement on Feb. 6, the day Lungo-Koehn informed union President Walter “Eddie” Buckley the city was reviewing the wave of sick calls between Feb. 2 and 6 that triggered “costs to the city of over $92,000 — $58,000 of which was overtime.”

Lungo-Koehn told councilors she thought the candidate could “really work” with the union in explaining “why something like the beginning of February is just not helpful.”

The Professional Fire Fighters of Massachusetts sent a letter earlier this week to local unions, “imploring members from outside departments to refrain from applying for Interim Fire Chief and Fire Chief positions” in Medford.

“He will no longer accept the position because he knows he’s going to get major pushback if he does accept,” Lungo-Koehn told the council.

The revelation came after Councilor George Scarpelli blasted the mayor and questioned whether she had a hire “pre-arranged.”

“If that’s the truth, that’s against the law,” he said. “If she’s already pre-approved somebody to come in that has declined the job today, that should be alarming to all of us.”

When asked if the mayor had the legal authority to offer the interim job to an outside candidate, Attorney Leah Barrault, whose firm represents Medford Firefighters Local 1032, said “No. That was illegal.”

Barrault, speaking to the Herald on Friday, outlined how she believes Lungo-Koehn has to comply with the civil service law by promoting from within the department. A city ordinance also highlights that in a chief’s absence, the senior deputy chief assumes leadership.

Promoting a firefighter to the chief’s position in the interim is complicated in Medford as the department “doesn’t have a civil service eligible list,” Lungo-Koehn told the Herald later Friday. Two years ago, four deputies signed up to take the required chief’s exam, but only Freedman ended up taking it, meaning he was the “only option” for the hire, the mayor said.

Taking a chief’s exam is required in order to be on the civil service eligible list for the position.

When there is no such list the “hiring department” could fill a vacancy on a “provisional basis” by appointing someone outside the department, according to the state Civil Service Commission.

The department for now is treating the vacant chief’s position similarly to when the chief would be on vacation by having a deputy in charge each day, Lungo-Koehn said. She expects to announce an acting chief sometime this week.

“The ordinance is trumped by the city charter which states that the mayor has the full authority to appoint all department heads,” Lungo-Koehn said. “The ordinance is almost like policies, bylaws whereas the charter is our constitution. That’s how it’s been explained to me by legal counsel.”

Not having an interim chief is putting the department at an “administrative standstill,” Buckley, the union president, said Friday. He believes the senior deputy chief should have already been appointed.

“Our Deputy Chiefs are experienced, capable, qualified and ready to step up, but without a defined singular leader, we are adrift,” Buckley said. “This decision should not be a political one, it’s a public safety need that this administration is refusing to address.”

Buckley declined to disclose what prompted the series of callouts. City officials have said while firefighters missed work in the morning, they returned to fulfill evening and night shifts.

The union is demanding the mayor to bargain with the deputy chiefs on the decision to press the chief’s responsibilities onto them, according to a letter Barrault wrote to Lungo-Koehn on Friday.

Firefighters filed an unfair labor practice complaint against Lungo-Koehn with the state Department of Labor Relations last Tuesday, alleging the mayor “defamed” the union on the city’s website and in the media, amongst other charges.

The complaint came after Lungo-Koehn announced the city’s review of the alleged “work stoppage.”

Specifically, 21 of 23 firefighters scheduled to work that Saturday called out sick, with three missing work “due to a sickness in the member’s family,” Lungo-Koehn has said. The wave began that Friday and lasted through the following Tuesday.

The mayor is looking to get out of civil service to make the process of filling the vacant chief’s position “more open and competitive.” For that to happen, the City Council would need to sign off on it before a home rule petition is sent to the State House.

Roughly 50 of more than 350 fire departments across the Bay State are in civil service.

When asked Friday whether she’s confident that the city department could form a quality candidate pool, Lungo-Koehn responded by combining hesitation with a touch of optimism.

“I believe there potentially could be a good candidate or two or three from the department, and I would want them to pursue that,” she said. “I am deeply concerned by the culture in the department. There was just a work stoppage over a five-day period where close to 70 people called out. I find that illegal.”