United Nations agencies must improve ways for staff to report harassment, retaliation and other forms of misconduct and safeguard whistleblowers who are prepared to reveal cases of abuse, an independent oversight body said on Monday.

Forty allegations of sexual exploitation and abuse were made during the last three months of 2017 alone against UN peacekeeping missions, agencies, funds and programmes and implementing partners, the world body said in February.

In a report issued on Monday, inspectors said several high-profile cases in UN organisations pointed to policies and practices that "appear to have failed to meet the high standards of accountability that these entities espouse."

"Over the past few years, there have been high-profile cases of whistleblowers from United Nations system organizations who have gone public for a variety of reasons, including a perceived lack of adequate action by their organization in response to their initial reporting of misconduct and/or retaliation," the Joint Inspection Unit said in a 110-page report.

In February 2018, the deputy head of the UN agency for HIV/AIDS did not seek to renew his term, although a sexual harassment allegation against him had been dismissed as unsubstantiated. A deputy director at the UN Children's Fund resigned saying he did not want coverage of his past mistakes to damage UNICEF.

The inspectors evaluated practices at 28 UN agencies and interviewed with more than 400 people, including 17 people who had reported wrongdoing, and conducted staff surveys. Among survey respondents, some 53 per cent of those who had witnessed misconduct or wrongdoing within the past five years had not reported it. Many did not do so "because they lacked confidence that confidentiality would be fully respected and that they would be effectively protected if they did report".

Ensuring anonymity and confidentiality were essential, especially given the hierarchical nature of the world body where a growing proportion of the workforce lack job security, the report said.

All agencies should have explicit provisions for reporting misconduct against the head of the organisation and the head of oversight to an independent channel, it added. Only three agencies had such provisions at the moment, it said.

Currently "not a single organisation’s policy fully met the requirements of all five best practices criteria", according to the report.