Justin Forsyth has resigned as Deputy Executive Director of UNICEF following accusations of inappropriate behaviour toward female staff while he was Chief Executive of Save the Children.

He announced on Thursday that he was tendering his resignation to UNICEF with a heavy heart, reports the Guardian.

Forsyth said he was not resigning because of the mistakes he had made while at the charity, but because of attempts to damage aid organisations and the humanitarian sector.

“I want to make clear I am not resigning from UNICEF because of the mistakes I made at Save the Children. They were dealt with through a proper process many years ago. I apologised unreservedly at the time and face to face. I apologise again,” Forsyth wrote.

“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. I am resigning because of the danger of damaging both UNICEF and Save the Children and our wider cause. Two organisations I truly love and cherish. I can’t let this happen.”

It emerged this week that Forsyth was accused of sending inappropriate texts and making comments to female staff about their appearance on separate occasions in 2011 and 2015 while he was the head of Save the Children.

After the allegations came to light, the former Labour party special adviser said he had issued an unreserved apology to the women involved at the time, and considered the matter closed.

UNICEF said it had accepted Forsyth’s resignation and thanked him for his work over the past two years, the Guardian reported.

Save the Children apologised on Tuesday to female employees who had previously complained about Forsyth’s behaviour, admitting the allegations were not properly dealt with at the time.

After inquiries into both allegations of inappropriate behaviour toward female staff, which were held in conjunction with an independent trustee, Forsyth apologised to the women concerned.

Forsyth’s resignation came after Brendan Cox, the widower of the murdered Labour MP Jo Cox, resigned from roles at charities he helped to set up in his wife’s memory following sexual harassment allegations while working at Save the Children.

After stepping down from his posts at More in Common and the Jo Cox Foundation, Cox said he made mistakes while working for Save the Children, and had behaved in a way that caused some women hurt and offence.

Cox and Forsyth worked together at 10 Downing Street under Gordon Brown before they both joined Save the Children.