Khyra Ishaq died in May 2008 from abuse and starvation
Six social workers at Birmingham City Council have been sacked over failings in the children's services department.
Its director Colin Tucker said they showed "no sign whatsoever" of adhering to expected standards.
The sacked staff were not involved in the case of Khyra Ishaq, the seven-year-old who starved to death in the city, he said.
The Unison union has called his remarks "misleading and irresponsible", adding he should stop looking for scapegoats.
A serious case review into the death from starvation and abuse of Khyra could lead to further sackings.
Eight children known to social services have died in the city in three years.
Mr Tucker was brought in after Ofsted severely criticised the running of the department.
It followed a number of child deaths, including that of Khyra whose mother and partner have been jailed for the death.
Angela Gordon was sentenced last week to 15 years for starving her daughter to death at their Birmingham home in 2008.
Her mother's partner, 31-year-old Junaid Abuhamza, was jailed indefinitely after his manslaughter plea was accepted.
Khyra was removed from school in December 2007 but when social workers attempted to call at her home they were either refused entry or the girl was presented to them on the doorstep and never seen alone by members of the department.
A High Court ruling into the case said that "in all probability" the girl would still have been alive if there had been "an adequate initial assessment by educational welfare services".
But, in an interview for BBC WM on Friday, Mr Tucker said the staff dismissals represented a new culture within his department.
"We are not appointing some staff and as well as that we have dismissed six staff in the last year," he said.
"There is a clear indication we are serious about our standards.
"They did not adhere to standards and expectations that we laid down.
"They showed no sign whatsoever that they were keen to do so, so we dismissed them."
He also revealed there were about 120 vacant posts which had been filled with agency staff.
A total of 750 social workers are employed by the department.
Asked on the BBC Today programme about the death of Khyra, he said: "In the profession, in the city, we are so upset about that it is untrue.
"Staff don't come into social work to harm children or to miss signs of when they're being abused or mistreated.
Experienced social workers are leaving Birmingham for other jobs and his comments are likely to speed up the exodus
Tony Rabaiotti, Unison
"Believe me, their motivation is to safeguard children. This has cast, and rightly so, a real shadow over this department for two years. But we can't turn the clock back."
When he first joined the department, which deals with about 2,000 cases, Mr Tucker admitted there had been mistakes in management and training, which led to the service entering special measures for the second time since 2002.
An audit by a council scrutiny committee identified failings, including a shortage of experienced staff, inadequate monitoring, excessive paperwork and too little time with children and families.
A total of three serious case reviews were now under way, Mr Tucker said.
Tony Rabaiotti, from Unison, said: "Mr Tucker should think more carefully before he opens his mouth and makes misleading and irresponsible claims.
"None of the social workers he claims he has sacked had anything to do with child care, let alone the tragic case of Khyra Ishaq.
"He may think that talking tough will hide Birmingham City Council's management from responsibility in the sad death of Khyra, but he is wrong.
"All it does is undermine staff confidence, which is already at an all time low. Experienced social workers are leaving Birmingham for other jobs and his comments are likely to speed up the exodus."
Hilton Dawson, Chief Executive of the British Association of Social Workers, said insufficient emphasis had been placed on training social workers in the past.
"Universities have not set the highest standards for social work," he said. "This is a failure of higher education and the regulators.
"We need a strong independent college of social work which drives the standard."
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