Amnesty International on Friday called on the Sudanese government to withdraw the charges against a woman journalist who risks 40 lashes for wearing trousers.
As a court in Khartoum prepares to resume the trial of Lubna Ahmed al-Hussein, Amnesty International said the law used to justify the flogging of women for wearing clothes deemed to be "indecent" should be repealed.
"The manner in which this law has been used against women is unacceptable, and the penalty called for by the law 'up to 40 lashes' abhorrent," said Tawanda Hondora, deputy director of Amnesty International's Africa Programme.
"The law is crafted in a way that makes it impossible to know what is decent or indecent," said Hondora.
"In practice, women are routinely arrested, detained, tried and then, on conviction, flogged simply because a police officer disapproves of their clothing.
"The law is also discriminatory, in that it is used disproportionately against women."
In 2003, the African Commission ordered Sudan to amend the article on the grounds that flogging amounted to state-sanctioned torture, after eight women brought a case against the government when they were arrested for publicly picnicking with male friends.
The eight were flogged in public using a wire and plastic whip, which reportedly left permanent scars on the women. The government has made no moves to amend the law since the Commission's decision.
"No one should be flogged. This is cruel, inhuman and degrading treatment and flies in the face of international law and common standards of human decency," said Hondora.
Hussein, a widow in her 30s, was charged with public indecency under Sudan's Islamic law after she was arrested in July along with 12 other women who were wearing trousers at a Khartoum restaurant.
Her trial has been adjourned to September 7 to determine whether the journalist, who works for a Sudanese newspaper as well as with the United Nations press office in Khartoum, has legal immunity.
Hussein has said she wants to be tried to challenge the law, and told a hearing that she wished to waive her UN immunity.
Ten women have already been whipped for the same offence -- including Christians -- and Hussein has said she will fight a guilty verdict and the law itself.
Hussein's case has triggered widespread outrage at home and abroad.
At the last hearing on August 4, Sudanese riot police used tear gas against hundreds of people demonstrating outside the Khartoum courtroom in protest at the trial, including activists from opposition parties.