The woman, who is a non-European national, is being supported in her legal claim by the charity Detention Action.
A pre-action letter has been sent to the office of Ms Braverman on behalf of the woman. The letter argues that the woman was unlawfully detained in “egregiously defective conditions” by Ms Braverman at the overcrowded processing site.
Law firm Duncan Lewis is representing both the charity and the female asylum seeker.
The challenge claims prolonged detention of asylum seekers at the site, failure to adhere to safeguarding measures for children, women and children are kept alongside unrelated adult men, inadequate legal advice, and exposure to infectious disease.
James Wilson, deputy director of Detention Action, said that they have taken legal action “out of serious concern for the welfare of thousands of people including children, still being detained at Manston for period far beyond legal limits”.
He continued: “We are calling on the home secretary to declare that anyone held at Manston for more than 24 hours is being detained unlawfully.
“We are also asking the home secretary to allow access to the facility for organisations qualified to provide support in immigration detention settings.”
Climate minister Graham Stuart admitted on Thursday that the government was holding asylum seekers at the Kent site illegally.
Asked on Sky News if he believed it was acceptable that people were being held illegally, he responded: “Obviously not. None of us are comfortable with it. We want it tackled, we want to get a grip, that’s exactly what the home secretary is focused on.”
Ms Braverman visitd Dover and Manston on Thursday. She is under growing pressure due to reports that she ignored legal advice about the deterioration of conditions at Manston.
Immigration minister Robert Jenrick said on Wednesday evening that the Home Office was facing a judicial review after reports of severe overcrowding at the site.
He said that the government had received “initial contact” for a judicial review.
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