Penny Mordaunt was dramatically confronted on stage by a protester who accused her of failing to give women a voice at a conference on sex abuse in the aid sector.

Alexia Pepper De Caires, a whistleblower and former Save the Children employee, approached the minister while she was delivering her speech in London on Thursday.

Pepper De Caires said: “A number of us would like to be on this platform but we have been kept back by DfID [Department for International Development] and your attempts to control women who are speaking out in this sector.”

She said she was angry and disgusted to learn of her former employer’s involvement in the safeguarding project when it was still under investigation by the Charity Commission for its handling of workplace sexual harassment allegations.

Save the Children is to sit on the advisory board of a new £10m global register of dangerous criminals working in the aid sector, launched by DfID and Interpol. The scheme will strengthen databases and vetting systems around the world, allowing charities to access records quickly, DfID said. The department is also to test a “humanitarian passport” scheme, which will vet NGO staff.

Pepper De Caires, who was eventually led away by officials as the assembled audience applauded her warmly, said: “We do not need fancy new systems, we do not need technology, we need systematic change. We need to understand the sexism, racism and abuse of power that happens from the very top of the leadership.”

Save the Children, which is banned from receiving aid funding while the investigation is ongoing, is not receiving money for the register.

The international safeguarding summit, held in London, was called in response to the Oxfam abuse scandal, exposed in February.

Mordaunt apologised to Pepper De Caires on stage and, alluding to a scathing attack on the summit contained in an open letter sent to her by campaign group Code Blue on Wednesday, offered the platform to the protester and her colleagues.

Mordaunt, who also said it would be appropriate if Pepper De Caires and her colleagues were given the closing slot at the summit, said: “I’m sorry, I wasn’t aware of the specific issue with Code Blue until today.”

Paula Donovan, the director of Code Blue, which campaigns to end impunity for sexual abuse in the aid sector, pulled out of the summit after branding the event’s objectives “cavalier and offensive”.

In an interview with the Guardian on Wednesday, Donovan said the conference amounted to an “abuse of power”, complaining that its agenda left no room for critics or analysis from civic society.

“You cannot have a dog and pony show with people in high level positions from institutions that are at the core of this problem standing up and declaring their shame and despair and their commitments and then that’s the end of the summit,” said Donovan.

“The UK government has been touting its leadership on tackling sexual exploitation in the aid sector for months, advertising an international summit with the objective of ‘Putting people first’. But then we were met with radio silence and with no information on the chosen experts or what kind of forum there would be.”

Mordaunt admitted to the conference “that we haven’t done all we should have done”, but added: “From my perspective, I think we have made good progress in the last few months.”

Responding to Donovan’s remarks, Mordaunt told the Guardian: “Code Blue have been part of one of our expert working groups and we have valued their input and we hoped they would attend the summit.

“Today is about taking very practical steps, which we have developed with the help of such organisations. We all need to work together because, unless we do, we will not make the changes, including the cultural changes, that are necessary. It is really important that every organisation feels able to contribute to that change.”

MPs accuse aid groups of 'abject failure' in tackling sexual abuse Read more

Later, Pepper De Caires said she felt Mordaunt’s offer of allowing her and other campaigners a platform was a “good step forward”. She felt she was “genuinely listening, to find out she could do in the moment”.

Commenting on the register, Kevin Watkins, chief executive of Save the Children, said: “We have one of the world’s top safeguarding experts in our organisation and he has been providing advice. It would be irresponsible and neglectful of us not to urge agencies like Interpol to engage with our sectors.”

Asmita Naik, the co-author of the 2002 west Africa sex for aid report, said the register would not solve the problem of sexual misconduct in the aid sector.

“We are going to spend £10m setting up a register and there is nothing to check,” said Naik. “Most of the cases we are talking about don’t result in convictions. In Haiti, it was heinous what they were doing, but transactional sex with adults is not a crime. It breached the code of conduct, but it is not a crime.”

Mordaunt said that the lack of convictions and prosecutions is something DfID is hoping to rectify.

More than 500 delegates are attending the summit, which according to DfID aims to “support survivors and victims, enhance accountability and drive up standards”.

Stephen Twigg, chairman of the UK parliament’s international development committee, which published a report on sexual abuse and exploitation earlier this year, said: “The dramatic intervention this morning reminds us what this conference is for, and that is the victims and survivors.

“As we set about establishing new mechanisms and processes to ensure an end to the sexual exploitation and abuse that has mired the sector for so long, we should also reflect. We need to look back and hear from those who have suffered, understand what they have been through and how previous approaches have failed them. Crucially, we need to include them in our conversations about how we move forward.”