The young women face being charged with "picking quarrels and provoking trouble", which could see them jailed for up to five years after they were detained by police in early March.
The vague charge of "provoking trouble" has been increasingly used by Chinese police under President Xi Jinping to detain and jail protestors for holding small-scale demonstrations.
The five women, Li Tingting, 25, Wei Tingting, 26, Wang Man, 32, Zheng Churan, 25, and Wu Rongrong, 30, had in recent years been linked to several stunts aiming to highlight issues such as domestic violence and the poor provision of women's toilets.
The activists are "young, kind-hearted, and full of a sense of responsibility to society," ten of their parents and spouses wrote in a letter to Beijing prosecutors that was posted online yesterday.
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"These five girls, who we care for and love deeply, have not made a mistake, let alone committed a crime," they said, adding "they have all striven to uphold our nation's basic policy of gender equality".
"Supporting gender equality and the interests of women is no crime!"
Police interrogations of the women, several of whom suffer from chronic health problems such as asthma and an unspecified heart condition, have focused on a 2012 stunt named "Occupy Men's Rooms", one of their lawyers Liang Xiaojun told AFP today, adding that prosecutors have until tomorrow to formally approve their arrest or police will be obliged to release them.
The parents said in their letter that the women "have been detained for over a month and we have not had a decent explanation". "Please restore their freedom and dignity as soon as possible!," they added.