Protesters chant slogans during a protest over the death of a woman who was detained by the morality police, in downtown Tehran, Iran. AP
The Union of Islamic Iran People's Party also called for the winding down of the morality police charged with enforcing the code following the death in their custody of 22-year-old Kurdish woman Mahsa Amini on September 16.
The party, which is led by former aides of reformist ex-president Mohammad Khatami who oversaw a thaw with the West between 1997 and 2005, called on the authorities to "prepare the legal elements necessary for the repeal of the law on mandatory hijab".
The party, which remains legal but is firmly outside the corridors of power, said Iran should announce an "official end to the activities of the morality police" and "authorise peaceful demonstrations."
It said an "impartial commission" should be set up to investigate the circumstances of Amini's death and called for the "immediate release of people recently detained".
At least 35 people have been killed and hundreds wounded in the protests that erupted after Amini's death, according to official figures. Hundreds more have been arrested, including reformist journalists and activists as well as demonstrators.
Under the law adopted in 1983, four years after Iran's Islamic revolution, all women, regardless of faith or nationality, must conceal their hair with a headscarf in public and wear loose fitting trousers under their coats.
The code has been widely skirted for decades, particularly in the major cities, but there have been periodic crackdowns.