(CNN) The International Committee of the Red Cross said 21 staff members have been dismissed or resigned for "paying for sexual services" since 2015.

An additional two staff members suspected of sexual misconduct didn't have their contracts renewed, Yves Daccord, the ICRC's director-general, said in a statement Friday.

"This behavior is a betrayal of the people and the communities we are there to serve. It is against human dignity and we should have been more vigilant in preventing this," Daccord said.

The revelation comes as other aid organizations have been hit by allegations of sexual harassment and exploitation by aid workers.

Daccord said staffers are "contractually bound by the ICRC's code of conduct" that bans the purchase of sexual services.

"This ban, in place since 2006, applies worldwide and at all times, including in locations where prostitution is legal, as the ICRC believes that staff paying for sex is incompatible with the values and mission of the organization."

This is a difficult but important day for the @ICRC. We are sharing information about sexual misconduct and other abuses of power in our organization: https://t.co/HaYIO9NPkP — Yves Daccord (@YDaccordICRC) February 23, 2018

The ICRC -- which has more than 17,000 staff members worldwide -- is concerned that some incidents have gone unreported while others have been reported but not dealt with correctly.

Daccord said he has "contacted other humanitarian organizations with the aim of addressing issues that require a collective effort," including stopping offenders from transferring from one agency to another.

"I am committed to fostering an ICRC culture that encourages staff to prevent, detect and report misconduct. All allegations are investigated. People must feel safe and empowered to raise concerns, and we have encouraged staff to make use of a dedicated, confidential email address to do so," he said.

"It is so important that the silence that has surrounded this issue has been shattered. This is a watershed moment for the humanitarian sector as a whole. We owe it to the people we serve to behave with absolute integrity."

'It's a large-scale problem'

British lawmakers this week heard details about sexual exploitation and abuse across the international aid sector. They met in special session to discuss the Oxfam scandal.

Kevin Watkins, chief executive of Save the Children , said the scandal surrounding Oxfam's operations in Haiti, where senior staff were found to have used prostitutes, isn't something that has just happened once.

JUST WATCHED Oxfam deputy chief resigns over sex scandal Replay More Videos ... MUST WATCH Oxfam deputy chief resigns over sex scandal 00:53

"We have to recognize that this is not the occasional bad apple but a structural sectorwide problem," Watkins told the House of Commons International Development Committee. "This is a real problem; it is systemic, it's a large-scale problem, and we have to fix it."

Other aid groups are grappling with sexual misconduct allegations in their ranks and have fired and disciplined staff.

The United Nations also has been hit with allegations of abuse. In 2016, the global organization said it had received 145 allegations of sexual exploitation and abuse -- 80 of which were associated with uniformed peacekeepers and 65 with civilian personnel.

A 2017 UN report on the issue said sexual exploitation has been a problem for years, compounded by weakly enforced hiring standards and lack of a screening system of candidates for a prior history of related misconduct.

Register for aid workers urged

Oxfam's embattled chief executive, Mark Goldring, apologized to British lawmakers for his organization's conduct in the aftermath of the 2010 Haiti earthquake.

He said Tuesday that about 7,000 people have stopped making regular donations to Oxfam since the Times of London newspaper first reported on the allegations. Goldring also said the charity has received around 26 fresh accusations of sexual abuse and exploitation since the scandal broke.

"It was common knowledge that this was going on across the sector, and no one knew how to deal with it," said Pauline Latham, a Conservative member of Parliament.

"I'm sure this is happening in Rohingya aid camps, I am sure it is happening round the world," she said, referring to the Muslim refugees who have fled to Bangladesh from Myanmar.

Latham urged the establishment of an international register for aid workers.

An internal Oxfam investigation from 2011 published this week confirmed seven of the charity's staff members were accused of using prostitutes at a residence in Haiti's capital, Port-au-Prince. Four were fired for gross misconduct, and three others were allowed to resign.

Haiti, which has criticized the UK charity for not notifying it of the findings, is now conducting its own investigation.

Winnie Byanyima, Oxfam International's executive director, said that women often end up being punished in countries such as Haiti where prostitution is illegal if authorities are notified.