While 15 people last night boarded the barge in Portland, Dorset, around 20 people did not take up the offer made on what the government has called a "no-choice basis".

Sky News has seen a letter sent by the Home Office to one of those people who stayed on dry land.

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It states: "Arrangements were made for you to travel from your accommodation... to alternative accommodation at the Bibby Stockholm in Portland on 7 August 2023.

"On 7 August you did not take up the offer of this accommodation.

"Please consider this letter a second notification to change your accommodation with arrangements in place to move you to the Bibby Stockholm, Portland on 8 August 2023.

"Accommodation is offered on a no-choice basis. Where asylum seekers fail to take up an offer of suitable accommodation without a reasonable explanation, there should be no expectation that alternative accommodation will be offered.

"If you do not travel tomorrow, on 8 August 2023, arrangements for ceasing the support that you are receiving from the Home Office may commence."

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It is not clear whether this means the person in question would be left homeless.

Asked if the government was breaking its legal duty to asylum seekers, Just Secretary Alex Chalk told Sky News: "Those who object to going on the barge can seek legal advice and try to resist it in the normal way and we will have those arguments played out in an independent court. That's absolutely right."

He described the barge as "basically safe and decent" and said the policy was about "fairness to the British taxpayer" to find a cheaper alternative to "four star hotels".

The Bibby Stockholm will ultimately hold 500 asylum seekers who are expected to board the barge gradually.

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On Monday, Cheryl Avery, the director of asylum accommodation at the Home Office, said the first cohort was made up of 15 people.

She added: "We have had a few challenges, but this is part of an ongoing structured process to bring a cohort of up to 500 people on board.

"There have been some challenges, some minor legal challenges, and I can't go to the detail of those, but accommodation is offered to all individuals on a no-choice basis - so we are looking at how we manage that going forward."

The Care4Calais group says about 20 asylum seekers did not board the barge because their transfers were "cancelled" due to legal challenges.

The charity claimed solicitors raised concerns about the suitability of the accommodation for people with disabilities, mental and physical health problems, as well as those who had fled torture and persecution.

Care4Calais chief executive Steve Smith said: "None of the asylum seekers we are supporting have gone to the Bibby Stockholm today as legal representatives have had their transfers cancelled.

"Amongst our clients are people who are disabled, who have survived torture and modern slavery and who have had traumatic experiences at sea. To house any human being in a 'quasi floating prison' like the Bibby Stockholm is inhumane. To try and do so with this group of people is unbelievably cruel. Even just receiving the notices is causing them a great deal of anxiety."

Steve Valdez-Symonds, Amnesty International UK's refugee and migrant rights director, said: "It seems there's nothing this government won't do to make people seeking asylum feel unwelcome and unsafe in this country.

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"Reminiscent of the prison hulks from the Victorian era, the Bibby Stockholm is an utterly shameful way to house people who've fled terror, conflict and persecution."

Sky News has approached the Home Office for comment.