Speaking to The Independent, the former Conservative cabinet minister urged the home secretary to stop holding people charged with no crime for months or even years – warning of its “devastating” psychological impact.
Two other former Tory ministers are demanding an end to the practice, in a vote expected in July, with others expected to join them in calling for a strict 28-day limit instead.
Mr Davis highlighted the case of Anna, a Chinese woman who fled her home after her husband was sentenced to death, as he stressed most detainees are “victims of human trafficking, sexual assault and torture”, not criminals.
Told she was being taken elsewhere in China, Anna was trafficked to the UK, “where she was forced into prostitution and several years of unpaid work – slavery by another name”.
She was then arrested during a raid and taken to Yarl’s Wood, one of 10 removal centres, where she was held indefinitely – one of 25,000 people held each year for immigration purposes.
“Anna’s story is not an isolated case,” Mr Davis said, adding: “There are all sorts of cruelties involved.
“These people, unlike people who are given a prison sentence, they don’t know when they are going to get out – and that is psychologically devastating.”
And he added: “I know only too well that all the advice the home secretary will be getting from the Home Office bureaucracy will be to resist this, but I ask them to look at the natural justice of this.
“We are a country which prides itself on its justice system. Yet, on the one hand we are supposedly campaigning against modern slavery, but – in the way we operate our holding centres – in some ways, we are exacerbating it.”
The criticism echoes research that trafficked women – instead of being offered help, as promised – are being locked up for possible deportation, inflicting more trauma.
Britain has faced growing criticism, including from the UN Human Rights Council, for being the only EU country without a statutory time limit for the detention of immigrants.
Survivors of torture, trafficking and rape are among those held in overcrowded centres – for months, or even years – where an investigation last year uncovered “widespread self-harm and attempted suicides”.
It would also introduce judicial oversight of detention after four days and establish much clearer criteria for taking someone into a removal centre.
Mr Mitchell has described indefinite detention as a “stain on our democracy”, while Mr Baker said he was “proud” to sign it, adding: “We must bring greater humanity to the immigration system.”
Sam Grant, policy manager at the campaign group Liberty, urged MPs to get behind the amendment, arguing coronavirus had laid bare the “inhumanity” of the detention system.
“The Immigration Bill is a chance for redemption, but that will only be achieved if MPs learn the lessons of the past and reform the immigration system so that humanity, dignity and respect sits at its core,” he said.