Video report by ITV News Correspondent Geraint Vincent
A former Save the Children boss has admitted he faced complaints about "inappropriate" behaviour during his time in charge.
Justin Forsyth, the charity's ex-chief executive, acknowledged he caused "hurt and offence" to three female colleagues during his tenure between 2010 and 2015.
Save the Children said separate investigations were carried out into each complaint which resulted in apologies from Mr Forsyth.
Unicef, where Mr Forsyth is the current deputy executive director, said it was "discussing" the matter with him.
Mr Forsyth, who worked for scandal-hit charity Oxfam between 1989 and 2004, is also a former special adviser to Tony Blair and Gordon Brown.
On Wednesday, Mr Forsyth issued a statement in which he admitted that complaints had been made against him in 2011 and 2015.
"I made some personal mistakes during my time at Save the Children," he said.
"I recognise that on a few occasions I had unsuitable and thoughtless conversations with colleagues, which I now know caused offence and hurt.
When this was brought to my attention on two separate occasions, I apologised unreservedly to the three colleagues involved. My apologies were accepted and I had thought the issue closed many years ago."
The concerns were handled through a mediation process and no formal complaint was made, he said.
Save the Children said the allegations related to "inappropriate behaviour and comments".
"In each case, the chairman instructed HR to manage the process in conjunction with an independent trustee," a spokesperson said.
"Two trustees carried out separate investigations into a total of three complaints made by female employees.
"Both reviews resulted in unreserved apologies from the CEO. All the parties agreed to this and the former CEO apologised to the women in question.
" At that time the matters were closed."
The spokesperson added that a fresh review into Save the Children's "organisational culture" was currently underway.
A Unicef spokesperson said: "We are aware of media reports related to past complaints against Justin Forsyth about events that occurred before he joined UNICEF.
"We welcome Mr. Forsyth’s decision to come forward and acknowledge past mistakes.
"We are discussing this matter with Mr. Forsyth and his former employer so we can take appropriate action."