Ex-Save the Children chief executive Justin Forsyth has resigned from Unicef as he says he does not want coverage of his past to "damage" the charities.
Mr Forsyth faced three complaints of inappropriate behaviour towards female staff before leaving Save the Children, the BBC reported this week.
He was accused of sending inappropriate texts and commenting on what young female staff were wearing.
He said he "apologised unreservedly" to the three workers at the time.
Mr Forsyth said the reason for his resignation as Unicef's deputy director was not because of what he described as the mistakes he made in his former role at Save the Children.
"They were dealt with through a proper process many years ago," he said in a statement.
"There is no doubt in my mind that some of the coverage around me is not just to (rightly) hold me to account, but also to attempt to do serious damage to our cause and the case for aid."
A statement from Unicef said it was grateful to Mr Forsyth for his work over the past two years.
An investigation by BBC Radio 4's PM programme found that the complaints against Mr Forsyth included women receiving a series of inappropriate texts and comments on how they looked, what they were wearing and how he felt about them.
If they did not respond, Mr Forsyth would follow up his messages with an email, asking if they had seen the text.
If they still did not respond, he would ask someone to send them to him for a "quick word".