Prince Charles is said to have privately called the UK government’s plans to send some illegal migrants to Rwanda “appalling”.
The first deportations under the contentious deal are expected to happen next week after the High Court ruled on Friday that a flight taking asylum seekers to the east African country can go ahead.
They will be the first migrants to be sent there to have their asylum claims processed since the government announced the policy in April.
A source heard the Prince of Wales expressing his opposition to the plans in a private conversation, according to The Times.
The prince, 73, is said to be particularly frustrated because he is due to represent the Queen at the Commonwealth heads of government meeting in the Rwandan capital Kigali this month.
A spokesperson for the prince stopped short of denying reports that he is said to be privately “disappointed” by the strategy. Clarence House insisted he had not tried to influence the government.
The judge at the High Court refused to grant an injunction sought by campaigners to block the one-way flight to Rwanda next Tuesday.
The campaign groups said they would appeal against the decision on Monday.
More than 30 people who arrived in the UK illegally are due to be on the plane to Rwanda the following day. The Home Office is set to schedule more flights this year.
Lawyers for nearly 100 migrants had submitted legal challenges asking to stay. Activists said the government’s policy was “not safe” and vowed to keep fighting, claiming that “forcibly deporting people… could profoundly harm their mental health and future”.
The Home Office argues the policy will deter people from making dangerous Channel crossings from France in flimsy small boats run by smugglers. Officials believe the removal plan is in the public interest and must not be stopped.
Welcoming the court ruling, Boris Johnson, the prime minister, tweeted: “We cannot allow people traffickers to put lives at risk and our world leading partnership will help break the business model of these ruthless criminals.”
Priti Patel, the home secretary, said: “We will not be deterred in breaking the deadly people smuggling trade and ultimately saving lives.”
She also insisted Rwanda is a “safe country and has previously been recognised for providing a safe haven for refugees”.
Up to 130 people have been notified they could be removed.
Two campaign groups – Detention Action and Care4Calais – joined the PCS Union and four individual asylum seekers in bringing legal action against the Home Office.
The judge, Jonathan Swift, ruled against the claim, saying: “There is a material public interest in the home secretary being able to implement immigration decisions.”
Graeme McGregor, from Detention Action, told Sky News: “We are obviously disappointed by this initial decision from the High Court. We have been granted application to appeal and that appeal will be going ahead on Monday so we’ll see what the outcome of that is.
“And we continue to be very concerned about the safety and welfare of those 30 or so people who are being threatened with being sent to Rwanda.”
Clare Moseley, founder of Care4Calais, said: “We are deeply concerned for the welfare of people who may be forcibly deported to Rwanda, a fate that could profoundly harm their mental health and future.”
The court was told that the UN refugee agency had a number of concerns about the asylum process in Rwanda, including discriminatory access to asylum – including for LGBT people – a lack of legal representation and interpreters, and difficulties in appealing.
In the first stage of legal action, brought on Friday, Raza Husain QC, for the claimants, told the court: “The system is not safe. It is not that it is not safe after July, it is just not safe.
“You may be arbitrarily denied access to it. If you do get into it, there are concerns about the impartiality of the decision-making.”
The Home Office has said five other people who were due to be deported will not be sent to Rwanda after they had their removal directions cancelled.
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The court was also told that a second flight may be scheduled for Thursday, which the Home Office denied.
The High Court is due to hear a further challenge to the policy on Monday, brought by Asylum Aid, a refugee charity, and supported by fellow campaign group Freedom From Torture.