Dhaka: The United Nations voiced its criticism on Thursday over a controversial new law in Bangladesh that allows underage children to be married off by their parents.

The new rule keeps the minimum marriageable age for males at 21 and for females at 18 but relaxes the restriction for ‘special circumstances’—including for girls who elope, are raped or bear children out of wedlock.

Rights groups fear without an age limit in these cases, underage children could be married off, undermining Bangladesh’s efforts to curb such unions and improve women’s health.

The UN’s child protection agency in Bangladesh said it ‘remains concerned’ about the special provision, and its potential impact on children’s wellbeing.

‘Marrying as a child has a lifelong impact on a person’s wellbeing. It limits opportunities and the chance to be a child,’ UNICEF’s representative in Bangladesh Edouard Beigbeder said in an email.

The Child Marriage Restraint Act, passed by parliament this week, replaced a law dating back to the British colonial period.

This dated legislation was largely ignored in poorer districts, where girls are married off in their early teenage years.

Beigbeder described the broader legislation, with its objective of preventing child marriage and providing sanction and remedies when cases did occur, as ‘a positive step forward’.

Child marriages have dropped from two-thirds of the total to around half between 2006 and 2013, UNICEF figures show.

Rights organisations warned this latest legal provision could unwind those gains, forcing new brides to drop out of school and work in conditions activists compare to child labour.