Birmingham council children's manager Colin Tucker goes
The director of Birmingham City Council's children's social care has left his post by "mutual agreement".
Colin Tucker was suspended in January partly over concerns, the authority said, about the slow pace of change and he left in April.
Children's social care was given a poor Ofsted rating in December 2010 after it was judged to be failing in July 2010.
A senior council source said Mr Tucker's department had not improved quickly enough.
They said that because of that, the council's future plans would not include him.
The source said Mr Tucker had not been disciplined because the council accepted he had done nothing wrong.
"He simply didn't work fast enough and children's welfare is so crucial we had to move faster and quicker and that did not involve Mr Tucker," the source added.
Mr Tucker joined the the council in 2009 and took over a department that had twice been put into special measures in seven years. His salary was £104,000 a year.
He has declined to comment on his departure.
The council is currently run by a Conservative and Liberal Democrat coalition.