A civil service trade union is taking the government to court over the plan to send asylum seekers to Rwanda.
The Safety of Rwanda Act, aimed at reviving the Rwanda plan to deport some asylum seekers to the east African country, was passed into law last week.
The policy was ruled unlawful by the Supreme Court, which the new Act directs ministers to overrule.
The Home Office expects deportation to begin as early as July.
The Rwanda policy seeks to deter people from crossing the Channel in small boats and the Home Office has started to detain people in preparation for deportation.
The FDA Union that represents civil servants has submitted an application for judicial review.
The union wants the High Court to decide whether a ministerial direction for a civil servant to ignore the previous court rulings would mean they were breaking the law and therefore the Civil Service Code of Conduct.
FDA general secretary Dave Penman said civil servants should never be placed in a position where they are conflicted between the instruction of ministers and the Civil Service Code.
“This is not an accident or down to poor drafting,” he said.
“It’s a political choice from the government, made not for the good of the country but to avoid upsetting either of the warring factions within its own party.”
The move is likely to cause further delays to deportations and is the first of what could be many legal challenges.
Each person being considered for forcible removal to Rwanda must be given at least seven days’ written notice of that intention and they have the right to launch a legal challenge.
The government had previously said it was aiming for flights to take off by the spring but now says this should happen in nine to 11 weeks.
The announcement about detentions beginning came the day before people in England go to the polls in local elections.
Labour has said it would scrap the Rwanda scheme if it wins the next election.
However, asked several times whether the party would release those detained as part of the policy, Labour’s deputy nation campaign coordinator Ellie Reeves would not say.
“We want to get people back to their own countries if their claims have failed which is why we would set up those return agreements and also recruit a thousand case workers,” she told BBC Radio 4’s World at One programme.
‘Causing fear, distress and great anxiety’
On Monday it emerged that most of the asylum seekers initially earmarked for deportation to Rwanda could not be immediately located.
Home Office documents show 5,700 asylum seekers have been identified in the initial cohort to be sent to Rwanda, but only “2,143 continue to report to the Home Office and can be located for detention”.
No 10 said it was “not accurate” to say the Home Office was unable to locate the others, but a government source admitted it was possible some could abscond before they were detained.
Responding to the initial detentions, Home Secretary James Cleverly said: “Our dedicated enforcement teams are working at pace to swiftly detain those who have no right to be here so we can get flights off the ground.”
Home Office director of enforcement Eddy Montgomery said teams were trained to ensure detentions were carried out safely.
He added: “It is vital that operational detail is kept to a minimum, to protect colleagues involved and those being detained, as well as ensuring we can deliver this large-scale operation as quickly as possible.”
The Home Office said it had increased detention capacity to more than 2,200 spaces and had 500 highly-trained escorts ready.
The department said commercial charters had also been booked and an airport had been put on standby.
Enver Solomon, chief executive of the Refugee Council, said: “The government’s move to detain people is causing fear, distress and great anxiety amongst men, women and children who have fled war and persecution to reach safety in the UK.”
He said the government should focus on processing asylum claims “efficiently and fairly”, rather than “headline-grabbing schemes that will waste time and resources”.
‘Pre-election gimmick’
It comes as new figures showed 268 people arrived in the UK across the Channel in five boats on Tuesday.
A total of 7,567 people made the journey from January to April, provisional Home Office figures show.
The figure is 27% higher than the number of arrivals recorded in the same period last year.
Meanwhile, a first failed asylum seeker has gone to Rwanda under a separate voluntary removals programme.
Under the scheme, announced in March, migrants whose claims are rejected are offered up to £3,000 to move to the east African country.
The Sun, which first reported the story, said the unnamed man was flown out of the UK on Monday on a commercial flight.
Shadow home secretary Yvette Cooper called news of the voluntary return a “pre-election gimmick,” adding taxpayers were “forking out £3,000 for a volunteer to board a plane”.
Liberal Democrat leader Sir Ed Davey said: “They’ve had to pay someone £3,000. There’s a suspicion out there that this is about an election – it’s not about seriously stopping the boats.”