A protester dramatically confronted the international development secretary to accuse her of silencing women trying to speak out about sex abuse by aid workers.
Alexia Pepper de Caires - a former whistleblower at Save the Children - walked onto the platform to tell Ms Mordaunt she was determined to “speak truth to power”.
“This platform is not for you today - it is for the people doing this,” she told her, warning she had announced “nothing” to tackle the crisis.
Ms Pepper de Caires drew applause from the international audience in London, while Ms Mordaunt listened to her calmly.
She said she was “disgusted” that Save the Children will play a major role in setting up a new global system of criminal records checks for aid workers, even while it remained under investigation itself.
Later, she said: “The signals were that a number of women who have been more radically vocal about what has been happening were not being reached out to.
“I thought all along that this conference needed to be more than just a shiny, glossy piece for the cameras and press to say all the right things are being done.
“It was dishonest, it is ineffective and it won't result in change.”
Ms Mordaunt told reporters she was unaware of the concerns and was “very sorry” that some people had felt excluded from the event.
“The only thing I could do today to rectify that - because I think it is important that their voices are heard - is to give them a platform,” she said.
“I personally didn't know of their concern until today. We will do everything we can to ensure that people are able to speak up, they are able to articulate their concerns.”
The international development secretary said that Save the Children had not received any government funding for its work on the new global register, being established with the help of Interpol.