The president has been accused of pandering to conservatives
Afghan President Hamid Karzai has been urged by the UN and Western aid agencies to abolish a new law that they say legalises rape within marriage.
They say that the law - signed by the president last month - limits the rights of women from the Shia minority.
A UN spokeswoman in Kabul told the BBC that it was seriously concerned about the potential impact of the law.
Aides to President Karzai insist that the new law has been introduced to provide more protection for Shia women.
But human rights activists say that the new law reverses many of the freedoms won by Afghan women in the seven years since the Taleban were driven from power.
The law has been described as 'oppressive' for women
They say it removes the right of women to refuse their husbands sex, unless they are ill.
Women will also need to get permission from their husbands if they want to leave their homes, unless there is an emergency.
Soraya Sobhrang from the Afghanistan Independent Human Rights Commission campaigned against the law. She has criticised long-standing Western silence over the issue which she said had been "disastrous for women's rights in Afghanistan".
"This law legalises all violence which happens against women in Afghanistan," she told the BBC. "They will lose their rights we have in our constitution."
The law covers members of Afghanistan's Shia minority, who make up 10% of the population.
It was rushed through parliament in February and has now been approved by President Hamid Karzai.
But the BBC's Mark Dummett in Kabul says that the final version has not yet been made public, and the president has not yet commented on it.
The law was backed by influential Shia clerics, and Shia political parties.
Defenders of the law say it is an improvement on the customary laws which normally decide family matters.
But critics like Member of Parliament Fawzia Koofi have accused the president of playing for votes.
"We have elections coming up in the summer and President Karzai's dependency on these fundamentalist groups is growing - and also he wants to have the support of the extremist Shia groups."
A separate family law for the Sunni majority is now also being drawn up. Activists fear that this too might be used to roll back Afghan women's hard-won freedoms.
A spokeswoman for the UN Development Fund for Women (Unifem) in Kabul told the BBC a "studied approach" is now required to determine the exact content of the new law.
"Unifem-Afghanistan remains seriously concerned about the potential impact of this law on the women of Afghanistan," the spokeswoman said.