If President Hamid Karzai does not veto the law – which would resitrict prosecutions for domestic and child abuse – within 15 days it will come into force

The European Union has called a draft Afghan law that would silence battered women a "backward step", while activists warn there are only two weeks to stop it coming into force.

The new criminal prosecution code bars relatives from testifying against each other, in effect putting justice out of reach for victims of domestic violence, forced marriage or child abuse.

A final draft was completed last week and has been sent by parliament to President Hamid Karzai, according to an international diplomat who is following the progress of the legislation.

Under the Afghan constitution, if Karzai does not veto it within 15 days, the law will come into force by default. The president's office did not respond to emails and calls seeking comment on his position. "I am very concerned that this new law would restrict prosecutions for domestic violence and child abuse in Afghanistan," the EU's foreign policy chief, Catherine Ashton, said.

"This would be a serious backward step in the justified and legitimate struggle for the rights of women and girls in Afghanistan. I urge the Afghan government to amend the language of article 26 of the criminal procedure code to avoid any misinterpretation, clarify their commitment to human rights and ensure consistency with international standards."

There has been a flurry of lobbying by diplomats since news of the draft and its implications broke last week. Much of it has been behind the scenes, with embassies saying they are wary of giving ammunition to conservatives in government, who argue that women's rights are a western imposition on Afghan culture.

But the Canadian government has also spoken out about the law, with the minister of state for foreign affairs, Lynne Yelich, telling Kabul that she was deeply concerned about its wider impact.

"This law would further limit protections for those who need it most, make it harder to hold perpetrators accountable for their actions and deny victims access to justice," she said.

Afghan activists, who have described the law as "a travesty", have stepped up pressure on Karzai to block or change it. They hope to repeat the success of a campaign in 2009 that forced the president to soften a family law enshrining marital rape as a husband's right.

But that was five years ago, and since then Karzai has presided over a strengthening of conservative forces. In the past year alone, parliament has blocked a law to curb violence against women and cut the quota for women on provincial councils, while the justice ministry floated a proposal to bring back stoning as a punishment for adultery.

Legal experts warned that, although news coverage has focused on how the law would affect women, in part because one of its backers is a vocal opponent of women's rights, it also has other alarming implications.

The brief sub-section of article 26 could be devastating to efforts to prosecute narcotics gangs, and if it comes into force would undermine the security forces and legal system, according to Kimberley Motley, a lawyer with a practice in Kabul.

"The law is not just [about] in-court testimony, but it says that witnesses cannot even be questioned, which takes a lot of authority away from the Afghan police, Afghan army, NDS [intelligence agency], and the attorney general's office," said Motley. Her work has included representing some of the most high-profile abused women, including the tortured child bride Sahar Gul, but also a range of other cases.

"It is a real mistake to just focus on how this law affects women," she said. "This law has the potential to make Afghanistan an absolute abysmal catastrophe as it relates to public order, rule of law and general common decency."