Kate Charlton, City Solicitor and Monitoring Officer at Birmingham City Council, is to leave the local authority on 30 September.
A statement on the council’s website said Charlton, who has worked for Birmingham for 11 years, was “leaving to pursue new career opportunities and to spend time with her family”.
The local authority also published a letter of apology to Charlton from Lady Mayoress Bushra Bi following comments made in an open letter in the Birmingham Mail regarding the running of full council.
Chief Executive Dawn Baxendale said: “I’d like to thank Kate for her advice and support over the years. I am sure the whole council will join me in wishing her well as she moves on to this next chapter of her life.
"She has been an important part of the senior leadership team at the council for a number of years, and her dedication and professionalism has been invaluable in supporting both politicians and her colleagues.”
The council said recruitment was underway for Charlton’s replacement.
Charlton said: "I would like to thank the council for acknowledging my contribution during the time I have worked for the council and I wish the politicians and colleagues continued success in the council’s journey."
Bushra Bi submitted her letter to the Birmingham Mail in response to criticism of the Lord Mayor, her father, at a public meeting that was later reported.
In her letter to Charlton, the Lady Mayoress wrote: “I apologise wholeheartedly for mentioning you in that letter. My response was based on emotion and from a position of misunderstanding.
“I regret any impact this may have had on you professionally. Please be assured that the Lord Mayor was in no way associated with the letter and continues to hold you in the highest regard.”