The United Nations expressed “grave concern” on Thursday about a new law issued by Afghanistan’s Taliban government on separation in marriage which includes provisions on child marriage, saying the code further entrenches discrimination against women and girls.

The government rejected the accusations, saying the decree follows Islamic law and insisting the country has already banned the forced marriage of girls.

Afghanistan’s justice ministry published Decree No 18 “on judicial separation of spouses” last week, which sets out rules for separation of a married couple.

Among its most controversial provisions, it says the silence of a girl reaching puberty can be interpreted as consent to marriage. It also includes a section on the separation of girls who reach puberty and are married, which “implies that child marriage is permitted”, the United Nations Assistance Mission in Afghanistan (UNAMA) said in a statement.

“This undermines the principle of free and full consent and failing to safeguard the best interests of the child,” it said.

The decree stipulates that a marriage can be ruled invalid “if a father or grandfather has given a minor girl or boy without any dowry, not enough dowry or obscene embezzlement”.

It also says that a girl given away in marriage by her father or grandfather to a man who “has not treated her with kindness or is well known for his bad choices … has the right to approach the court to cancel the marriage contract upon reaching puberty”.