Human Rights Watch (HRW) called for international donors to withhold funding if the Government goes ahead with the plan.
Death by stoning was used as a punishment for adultery during Taliban rule, a brutal period which included bans on radio, television and music, and ended in 2001 when Nato forces seized Kabul.
Since then, human rights - and women's rights, in particular - have frequently been cited as a measure of progress under Hamid Karzai's Government.
His Government signed up to international human rights conventions.
In May, the country's lower chamber revised electoral law, ditching the guarantee that at least a quarter of seats in each of 34 provincial councils be reserved for women.
And Parliament has never ratified a long-awaited law setting penalties for rape, child marriage and the giving of girls to resolve disputes.