Suella Braverman is ploughing ahead with contentious plans to house more than 500 asylum seekers in a giant barge despite the threat of legal action.
The Home Office proposal has been heavily criticised and a Tory MP says a challenge in the courts is being considered in order to change the Home Secretary's mind.
After the move was confirmed, campaigners dismissed it as "political theatre" and called for an end to "ministerial cruelty".
And the British Red Cross said the barge was inappropriate and called for a "more effective and compassionate asylum system".
The Government says it intends to use the three-storey Bibby Stockholm vessel, docked at Portland Port in Dorset, at a reported cost of £20,000 a day.
The lease for the barge, which was built in 1976, will be for at least 18 months.
Shadow Home Secretary Yvette Cooper said the decision is a sign of the Tory failure to clear the asylum backlog.
The move is being considered as a temporary solution after years of Tory failure to process applications, which has saddled taxpayer with a £6 million-a-day bill for hotels.
But Ms Braverman faces a backlash, even within the Tory hierarchy, with the Conservative-run Dorset Council against the move and MP Richard Drax saying a legal challenge was being considered.
Mr Drax, who represents South Dorset, said the barge was being "dumped on our door" without any consultation by the Home Office.
Christina Marriott, the British Red Cross’s executive director of strategy and communications, said: "Docked barges, which are isolated from the wider community, do not offer the supportive environment that people coping with the trauma of having to flee their homes need.
“People are being housed in inappropriate accommodation because of the asylum backlog, with slow decision making on cases leaving 160,000 stuck in the system and living in limbo. We need a more effective and compassionate asylum system, one that supports people to integrate into a community so they can find safety and live in dignity.”
And Steve Valdez-Symonds, Amnesty International UK’s Refugee and Migrant Rights Director, said: “Confining hundreds of people in isolation on a barge is just more of the political theatre that the Government has created to obscure its gross mismanagement of the asylum system.
“Along with the disastrous Rwanda scheme, all talk of barges, cruise ships and former military barracks should be abandoned."
He added: “Instead of more ministerial cruelty, we need sweeping asylum reforms, with an emphasis on deciding claims fairly and efficiently, acting on those decisions, eliminating wasteful repeat reconsiderations of decisions that people are entitled to asylum, and making a real effort to reduce huge backlogs and unreasonable Home Office workloads.”
Ms Cooper said: "This announcement is a sign of the Conservatives' total failure to clear the asylum backlog, tackle the criminal smuggling gangs or get any kind of grip on the system.
"This barge is in addition to hotels, not instead of them and is still more than twice as expensive as normal asylum accommodation. It will house just 0.3% of the current Tory backlog which has sky-rocketed and is continuing to grow under the Conservatives.
"Until the Government takes serious action to clear the backlog, this problem is going to keep getting worse with more people in costly accommodation, not less. Their new legislation only makes the problem worse."
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The Home Office faces opposition from within Tory circles, with South Dorset MP Mr Drax saying: "Every option's being looked at including legal action.
"We want to get this consigned to the dustbin before anything's signed. We want to activate ourselves and say look Home Secretary, sorry, this is not the right place, can you please cancel this."
He said he was worried about the practicality of keeping hundreds of vulnerable people in a "very, very restricted area".
This would put added pressure on the port's "very small" police force, he said.
"They will be allowed out on a bus every so often but in effect will be incarcerated for quite a lot of the time," Mr Drax stated.
He also claimed it would impact businesses in the seaside resort of Weymouth, adding: "This is an extremely sensitive area which relies heavily on summer trade, I cannot see how this is going to be anything but detrimental."
Confirming the use of the barge, immigration minister Robert Jenrick said: "The Home Secretary and I have been clear that the use of expensive hotels to house those making unnecessary and dangerous journeys must stop.
"We will not elevate the interests of illegal migrants over the British people we are elected to serve.
"We have to use alternative accommodation options, as our European neighbours are doing - including the use of barges and ferries to save the British taxpayer money and to prevent the UK becoming a magnet for asylum shoppers in Europe.
"All accommodation will meet our legal obligations and we will work closely with the local community to address their concerns, including through financial support."
Portland Port confirmed it had been selected by the Home Office as a site for a migrant barge, but Dorset Council said it has "serious concerns about the suitability of the location for this facility".
The 93-metre long barge can house up to 506 people in its 222 bedrooms.
Ms Braverman is facing growing disquiet in Tory circles. Today Caroline Brook, a Conservative councillor in Winchester where the Home Secretary is hoping to be selected as the parliamentary candidate, said she would "struggle" to knock on doors and campaign for her.
Ms Brook told Times Radio she "disagrees fundamentally" with some of Ms Braverman's views.
She said: "I'd struggle. I'd struggle. Yeah, I would, I'd struggle. I disagree fundamentally with her on some of her views. I'm sure in time I'd get to know her. And she'd actually pick up the phone and speak to me which she hasn't during the whole process."
"The boat policy, for example, I struggle with the way that's being implemented.
"I'm not convinced that doing something that is borderline anti international looking after international people, I fundamentally don't think that we should border that and go 'we think it's it's legal', because that jeopardises our people who live abroad, our residents who live abroad because if we're straddling that we think it's legal it might not quite be, why should they treat our people in their countries fairly?
"So fundamentally, I disagree on some real key points."
