A civil service union is taking the government to court over plans to send some asylum seekers to Rwanda.
Under the Rwanda Security Act, which was passed into law last week, the minister can ignore an order issued by the European Court of Human Rights (ECHR).
The FDA union said the directive to do so would violate international law and violate the Civil Service Code.
The government said the advice from its head of rights and ethics was that it did not breach the protocol.
In a letter It has been published on the website of the government. Darren Tierney wrote: “In implementing the decision, civil servants will act in accordance with the Civil Service Code, which states that once decisions are made, they must not be disappointed in implementing policies.”
“They shall act in accordance with the Act, which is an Act enacted by Parliament under which the Minister's specifically authorized and affirmed discretion shall be exercised.”
The Home Office expects flights to Rwanda to start in July.
Rwandan policy sought to prevent crossing the English Channel in small boats and the Home Office began detaining people in preparation for deportation.
The FDA, which represents civil servants, has submitted an application for judicial review on whether a minister can direct a civil servant to ignore an ECHR ruling.
The union wants the High Court to decide whether the civil servant violated the law and therefore the civil service code of conduct.
FDA Secretary General Dave Penman said civil servants should never be in a position of conflict between ministerial directives and civil service ethics.
“It wasn't an accident or bad drafting,” he said.
“It was a political choice by the government, made not in the interest of the country but to avoid upsetting both of the warring factions within its own party.”
The move could further delay deportations and is the first of several legal challenges.
Earlier, the Home Office confirmed that “continuing operations at national level” were underway to detain people across the country ahead of forced removal.
“The first illegal immigrants removed to Rwanda have now been detained,” a spokesman said, calling the detentions “another major milestone” in the Rwandan program.
Photos and video were released of immigration enforcement officers detaining several immigrants at different residences, who were then taken away in handcuffs and loaded into secure vehicles.
Each person considered for forcible removal to Rwanda must be given at least seven days' written notice of the intention, and has the right to initiate a legal challenge.
The government previously said it was aiming for flights to take off in the spring, but now says it could happen in nine to 11 weeks.
The announcement of the detentions came a day before people went to the polls in local elections in England.
Labor has said it will scrap the Rwanda program if it wins the next election.
However, Ellie Reeves, Labor's deputy national campaign co-ordinator, said no when asked repeatedly if the party would release those detained as part of the policy.
“If their claims fail, we want to return people to their countries of origin, which is why we will set up return agreements and add a thousand caseworkers,” he told BBC Radio 4's World at One programme.
'Causes fear, distress and great anxiety'
Home Office documents show that 5,700 asylum seekers were identified in the initial group to be sent to Rwanda, but “only 2,143 regularly report to the Home Office and can be detained”.
Number 10 said it was “not accurate” to say the Home Office could not find the others, but a government source admitted it was possible some absconded before they were detained.
Responding to the initial detention, Home Secretary James said wisely: “Our dedicated enforcement teams are working at speed to quickly detain people who have no right to be here, so we can get planes off the ground.”
The teams are trained to ensure detentions are carried out safely, said Eddie Montgomery, director of the Department of the Interior's Office of Enforcement.
He added: “In order to protect the colleagues and detainees involved and to ensure this large-scale operation can be delivered as quickly as possible, it is vital that operational details are kept to a minimum.”
The Home Office said it had increased its detention capacity to more than 2,200 places and had 500 highly trained escorts on standby.
Commercial charters have also been registered and the airport has been put on standby, the department said.
Enver Salomon, chief executive of the Refugee Council, said: “The government's move to detain people is causing fear, distress and great anxiety among men, women and children who have faced war and persecution to reach safety in Britain.”
He said the government should focus on processing asylum claims “efficiently and fairly” rather than “head-on schemes that waste time and resources”.
'Pre-election gimmick'
New figures show 268 people arrived in the UK via the Channel on five boats on Tuesday.
Provisional Home Office figures show a total of 7,567 people traveled between January and April.
This figure is 27% higher than the number of visits recorded during the same period last year.
Meanwhile, the first failed asylum seeker has gone to Rwanda under a separate voluntary removal scheme.
Under the scheme, announced in March, migrants whose claims have been rejected will be given up to £3,000 to travel to the East African country.
Shadow Home Secretary Yvette Cooper called news of the voluntary withdrawal a “pre-election gimmick” and said taxpayers were “paying £3,000 for a volunteer to get on a plane”.
Liberal Democrat leader Sir Ed Davey said: “They had to pay £3,000 to someone. This is doubtless about an election – it's not about seriously stopping the boats.”
