(CNN) -- Thirteen Boston deputy fire chiefs have signed a letter of "no confidence" in Fire Chief Steve Abraira regarding his handling of the Boston Marathon bombings, according to the letter, which CNN independently obtained from a deputy chief who signed it but requested anonymity.
The deputy chiefs wrote of their displeasure to Boston Mayor Thomas Menino on April 26, according to the letter.
"You can unequivocally consider this letter a vote of no confidence in Chief Abraira," the deputy chiefs wrote in the letter. They said the chief failed to assume command responsibility or show any leadership at the scene.
"Despite the fact that the members of the BFD command staff have become accustomed to this 'ghost fire chief,' nothing prepared us for his actions, actually inactions, on the day of the horrific terrorist attack at the Boston Marathon," the letter reads.
"At a time when the City of Boston needed every first responder to take decisive action, Chief Abraira failed to get involved in operational decision-making or show any leadership," the letter continues.
In the letter, the deputies describe an e-mail that Abraira sent to all department members, saying that when he arrived at the scene, "it was clear that our Command Officer had the incident well in hand and that our department was fully active in a support role with our law enforcement partners."
The deputies call Abraira's argument "illogical" and "mere rationalization to justify his behavior," saying that when Abraira arrived, the Boston Fire Department was "still heavily involved in the incident" because of the possibility of "second explosions," "additional suspicious packages" and "structural stability concern of buildings," among other issues.
But Abraira defended his actions to CNN.
"In their estimation, they believe that if you don't assume command, you don't have responsibility there for what goes on," he said. "I tried to explain to them, if I'm on the scene, I'm still responsible. That's it. But they don't believe it."
The chief told The Boston Globe that he was comfortable with the way his commanders were handling the incident.
"The nationally accepted practice is that you only take command (as chief) if there's something going wrong or if you can strengthen the command position or if it's overwhelming for the incident commander, and none of those things were in fact happening," he told the paper.
The president of the Boston City Council, Steve Murphy, told CNN Wednesday that he was at the finish line shortly after the bombings and "personally I didn't see anything but selfless heroic acts on the part of the fire, EMT and police personnel."
But Murphy added, "if all 13 of our district chiefs are expressing no confidence then that concerns me." He said if the mayor did not act in response to the letter that the City Council, which funds the fire department, would look into the functioning of fire department command during upcoming budget discussions.
The twin blasts at the end of the Boston Marathon on April 15 killed three people and wounded more than 260 others. Six people remained hospitalized Wednesday, according to a CNN count.
One of two bombing suspects, Tamerlan Tsarnaev, died after a gunfight with authorities four days later. After much secrecy and protest, he was buried in a rural Virginia cemetery this month.
Police took his brother, Dzhokhar Tsarnaev, into custody on April 19 after finding him hiding in a boat in the backyard of a Watertown, Massachusetts, home.
He has been charged with using a weapon of mass destruction and malicious destruction of property causing death.
Tsarnaev is being held at Federal Medical Center Devens.
CNN's Joe Sterling and Lawrence Crook III contributed to this report.