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 Monday.
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. 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 practice 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."
Social acceptance is the most commonly cited reason for continuing genital cutting, even though it is considered a violation of human rights, UNICEF found.
The practice "is becoming less common in slightly more than half of the 29 countries studied," said the report, noting that "overall support for the practice is declining."
The ritual is practiced 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 per cent of females aged 15-49 have been cut, followed by 96 per cent in Guinea, 93 per cent in Djibouti and 91 per cent 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.
The report also found that even though the genital cutting is often considered a form of patriarchal control, there is a similar level of support among men and women for stopping it.
"Social acceptance is the most frequently mentioned reason for supporting the continuation of the practice," said report author Claudia Cappa, a UNICEF statistics specialist.
"This is the main reason why women -- mothers still have their daughters cut. And this is done sometimes even if they think the practice should be discontinued," she told reporters in Washington.
Cappa said that research shows that "many boys and men also want this practice to end and this number is growing."
UNICEF said the ritual should be open to greater public scrutiny, and called for groups that still practice it to be exposed more to those that do not.
"The challenge now is to let girls and women, boys and men speak out loudly and clearly and announce they want this harmful practice abandoned," said Geeta Rao Gupta, UNICEF Deputy Executive Director.
Last year, the UN General Assembly adopted a non-binding resolution to intensify global efforts to eliminate female genital mutilation.
Francesca Moneti, UNICEF senior child protection specialist, said generations of tradition can be difficult to overcome.
"It is something that has just always been there," she said.
"You need to have a moment of discussion where people can come out and say that they don't support it."