Justin Forsyth resigned as deputy executive director of Unicef in NY after his former colleagues complained about his conduct.
Forsyth states that he "apologized unreservedly" to the three workers at time.
In a statement yesterday Mr Forsyth said: "With heavy heart, I am today tendering my resignation to Unicef as deputy executive director".
"I am resigning because of the danger of damaging both UNICEF and Save the Children and our wider cause".
"They were dealt with through a proper process many years ago", his statement said.
"Two organisations I truly love and cherish".
Forsyth had faced three complaints of inappropriate behaviour towards female staff himself before he quit as chief executive of Save The Children in 2015.
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"We have sometimes failed, but I feel privileged to have had the chance to help millions of children", Forsyth said. The final report will be shared with the Charity Commission, and made available to the government and all members of staff, Save the Children said.
The disclosures regarding Mr Forsyth were made public after Brendan Cox, the widower of the murdered MP Jo Cox, admitted that he made "mistakes" when he was working at Save the Children.
Executive Director Anthony Lake (3rd L) stands with Justin Forsyth (L) - the chief executive of Save the Children - as they visit a school inside a refugee camp in Zahle, Beqaa Valley, Lebanon, March 14, 2014.
If they did not respond, Mr Forsyth would follow up his messages with an email, asking if they had seen the text.
Save the Children said it had commissioned "a root and branch review of the organisational culture" at the charity "addressing any behavioural challenges among senior leadership". "We are discussing this matter with Mr. Forsyth and his former employer so we can take appropriate action".
"There have been no such complaints concerning Mr Forsyth at Unicef", he added.