Campaigners are threatening legal action against Suella Braverman over conditions at the Manston migrant holding centre.
Lawyers on behalf of Detention Action and a woman held at Manston sent an urgent pre-action letter to the Home Office on Tuesday, the charity said, representing the first action against the Home Secretary for “the unlawful treatment of people held at the facility”.
Immigration minister Robert Jenrick previously confirmed the Government had received “initial contact for a judicial review” over Manston, but could not comment on who was behind the challenge for legal reasons.
He said the move was “not unusual” as it concerned a “highly litigious area of policy”.
The pre-action letter, sent by Duncan Lewis solicitors, said the woman - from a non-European country - “was unlawfully detained by the Home Secretary at the Manston facility in egregiously defective conditions”.
The complaint also includes “serious threats to the safety of children”, the charity said.
Concerns raised by the woman and the charity about the site near Ramsgate include:
The routine prolongation of detention beyond statutory time limits;
Failure to adhere to essential safeguarding measures for children;
Women and children sleeping alongside adult men to whom they are unrelated;
Inadequate or non-existent access to legal advice for those detained
Exposure to infectious diseases due to overcrowding and poor sanitation
According to reports, the woman at the centre of the legal challenge against the Home Office was detained at Manston for three weeks.Speaking to ITV's Political Editor on Wednesday, Immigration Minister Robert Jenrick said: "There are two competing duties here.
"One is to ensure that Manston operates in a legal way which means people don't stay for more than 24 hours. There's also a duty not to leave people destitute."
Deputy director of Detention Action James Wilson said: “We have taken this action out of serious concern for the welfare of thousands of people, including children, still being detained at Manston for periods far beyond legal limits.
“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 that the Home Secretary allow access to the facility for organisations qualified to provide support in immigration detention settings.”
A spokesman for the Home Office said: "Manston remains resourced and equipped to process migrants securely and we will provide alternative accommodation as soon as possible."