More than 125 million girls and women alive today have undergone female genital mutilation, and 30 million more girls are at risk in the next decade, UNICEF said.
Although genital cutting is on the decline, the practice remains "almost universal" in some countries, said the report by the United Nations Children's Fund, released on Monday.
The report compiles 20 years of data across 29 countries in Africa and the Middle East.
The tradition involves removal of some or all of a female's external genitalia. It can include cutting out the clitoris and sometimes sewing together the labia.
Laws are not enough to stop the practise entirely, and more people must speak out in order to eliminate it among certain ethnic groups and communities, the researchers said.
The tradition remains "remarkably persistent, despite nearly a century of attempts to eliminate it," it said.
"As many as 30 million girls are at risk of being cut over the next decade if current trends persist."
'No discernible decline'
Social acceptance is the most commonly cited reason for continuing genital cutting, even though it is considered a violation of human rights, UNICEF found.
[There was] no discernible decline in countries such as Chad, Gambia, Mali, Senegal, Sudan or Yemen
Thepractisee "is becoming less common in slightly more than half of the 29 countries studied," said the report, noting that "overall support for thepractisee is declining".
The ritual ispractisedd by various faiths, including Christians, Muslims and followers of African traditional religions. Some believe it improves a girl's marriage prospects, or that it is more aesthetically pleasing.
The report found the highest rates in Somalia, where 98 percent of females aged 15-49 have been cut, followed by 96 percent in Guinea, 93 percent in Djibouti and 91 percent in Egypt.
The amount of data for analysis varied from country to country, but declines were apparent over time in countries like Kenya and Tanzania, where women in their 40s were three times as likely to have undergone cutting as girls 15-19.
Prevalence of genital cutting among teenage girls has dropped by about half in Benin, the Central African Republic, Iraq, Liberia and Nigeria.
However, there was "no discernible decline in countries such as Chad, Gambia, Mali, Senegal, Sudan or Yemen," it said.