One-third of United Nations staff and contractors say they experienced sexual harassment over the past two years, according to a new report released by the organisation.

The online survey, carried out by Deloitte in November and published on Tuesday, was completed by 30,364 people from the UN and its agencies - just 17 percent of those eligible.

In a letter to staff, Secretary-General Antonio Guterres described the response rate as "moderately low".

"This tells me two things: first - that we still have a long way to go before we are able to fully and openly discuss sexual harassment; and second - that there may also be an ongoing sense of mistrust, perceptions of inaction and lack of accountability," Guterres wrote, according to Reuters.

The survey comes amid the wider "Me Too" movement around the world against sexual harassment and assault.

It also follows UN efforts to increase transparency and strengthen how it deals with such accusations over the past few years after a string of sexual exploitation and abuse accusations against the world body's peacekeepers in Africa.

The head of the UN Programme on HIV/AIDS (UNAIDS) is also stepping down in June, six months before his term ends, after an independent panel said that his "defective leadership" tolerated "a culture of harassment, including sexual harassment, bullying, and abuse of power."

'Sobering statistics'

According to the report, 21.7 percent of respondents said they were subjected to sexual stories or offensive jokes, 14.2 percent received offensive remarks about their appearance, body or sexual activities and 13 percent were targeted by unwelcome attempts to draw them into a discussion on sexual matters.

Some 10.9 percent said they endured gestures or the use of body language of a sexual nature, which embarrassed or offended them, and 10.1 percent were touched in a way that made them feel uncomfortable.

More than half of those who said they had experienced sexual harassment said it happened in an office environment, while 17.1 percent said it happened at a work-related social event. Two out of three harassers were male, according to the survey.

Only one in three people said they took action after experiencing sexual harassment.

Guterres said the report contained "some sobering statistics and evidence of what needs to change to make a harassment-free workplace real for all of us."

"As an organisation founded on equality, dignity and human rights, we must lead by example and set the standard," he said.