Despite being illegal in Nepal since 1963, "police rarely act to prevent child marriage or bring charges," the New York-based Human Rights Watch (HRW) said Thursday.
In its report "Our Time to Sing and Play," the NGO said government officials often officially register child marriages, even though it is a crime.
HRW said there was little evidence that the Nepalese government was trying to prevent child marriage or mitigate the harm that married children experience.
"Many children in Nepal - both girls and boys - are seeing their futures stolen from them," said senior women's rights researcher Heather Barr in a statement.
DW also reported on child marriages in Nepal earlier this year.
HRW's report, based on more than 100 interviews with people who had been married as children, said girls were being denied an education and faced domestic violence. Many were also forced to have children before their bodies were ready, HRW said.
"My parents wanted me to marry someone they had chosen. There were two or three proposals. My parents liked them, but I didn't," said Sunita Lam, 16, who eloped with a man she had only spoken to on the phone.
Up to 37 percent of Nepalese girls marry before they are 18, according to United Nations figures, in part due to traditional practices and poverty.
HRW said last year's massive earthquake, which killed 9,000 people, has not helped reduce the number, having left thousands of families homeless and many children as orphans.
The report said child marriage is prevalent in the country's Dalit or indigenous communities, where dowry practices, social pressure, and a lack of access to education all contribute to its acceptance.
Family pressure means girls are unlikely to complain to the authorities if they know their marriage is illegal. Even if they do police are reluctant to act, said Rashmila Shakya of Child Workers In Nepal, a children's rights organization.
"Police and authorities give least priority to child marriage cases because it is just accepted reality for them," Shakya said.
The Nepalese government insisted it has made significant progress in stopping child marriage and has new policies and laws to address the issue, including a new law that says both men and women have to be 20 before they can legally marry.
"For the first time child marriage is protected by the constitution, which says it is illegal," said Dr. Kiran Rupakhetee, from the Ministry of Women, Children and Social Welfare, adding the government this year also adopted a national strategy plan to end child marriages.
Violators can be jailed for three years and fined 10,000 rupees ($95), which is more than the monthly salary for many people.
mm/jil (AFP, AP)