Home Secretary Priti Patel has been asked to provide details of controversial plans to send asylum seekers to Rwanda ahead of a potential legal challenge.

A “world-first” agreement with the east African nation, which will see it receive asylum seekers deemed by the UK to have arrived “illegally” and therefore inadmissible under new immigration rules, was signed earlier this month.

The latest step in the Government’s plan to curb Channel crossings and overhaul the asylum system has drawn criticism from across the political spectrum, including from the Archbishop of Canterbury Justin Welby.

The charity Freedom From Torture, which supports survivors of torture who are often asylum seekers and refugees, wrote to the Home Office on Wednesday requesting further information, with a view to bringing a High Court claim over the policy.

A letter from the charity’s legal representatives, Leigh Day, says that, while a memorandum of understanding between the UK and Rwanda has been published, information about the policy has not been made publicly available.

It also says the charity has “serious concerns” about the policy and in due course plans to bring a judicial review.

The letter says: “This material is properly necessary in order for the claimant to understand the terms and scope of the policy, and to allow it to properly identify the issues in relation to the policy, including for the purposes of the letter before claim.

“For the avoidance of doubt, we write this letter in contemplation of judicial review proceedings and it therefore engages the duty of candour.”

The charity is asking for any document which sets out the policy of relocating asylum seekers to Rwanda, any guidance or rules provided to Home Office staff or other UK officials, any documents relating to co-operation with Rwanda, and any equality impact or risk assessments carried out in relation to the policy.

The letter requests that any response is sent by 4pm on May 4 and the charity plans to crowdfund to cover legal costs of the case.

Sonya Sceats, chief executive of Freedom From Torture, said: “The outpouring of compassion for those fleeing Ukraine and Afghanistan has shown that the public wants people seeking safety to be welcomed.

“But instead, this Government is planning to ship refugees halfway around the world to Rwanda.

“We shouldn’t have to resort to legal action for this Government to treat refugees with basic human dignity – but here we are again.

“This cruel plan is not only deeply immoral and likely unlawful, it would also deny torture survivors and others access to vital trauma services like those provided by Freedom From Torture.

“Up and down the country, people are beginning to mobilise against this Government’s cynical efforts to stoke fear and xenophobia against refugees.

“This action is one part of a wider fight by the caring public to tell the Government that this is not in our name.”

The charity was one of a number of groups involved in a challenge due to be heard next week against the Home Secretary over plans to “push back” migrants in boats crossing the Channel, but the planned policy was withdrawn on Sunday.

In a speech earlier this month outlining the Rwanda agreement, Ms Patel said: “The British people are fair and generous when it comes to helping those in need, but the persistent circumventing of our laws and immigration rules and the reality of a system that is open to gaming and criminal exploitation has eroded public support for Britain’s asylum system and those that genuinely need access to it.

“Putting evil people smugglers out of business is a moral imperative. It requires us to use every tool at our disposal – and also to find new solutions.

“That is why today’s migration and economic development partnership with Rwanda is such a major milestone.

“This agreement fully complies with all international and national law, and as part of this ground-breaking agreement, the UK is making a substantial investment in the economic development of Rwanda.”