The Home Office lawyers, who are due to respond later, are expected to argue that the plans to remove migrants to Rwanda “pursue an important public interest.”
They say the removals are intended to deter people from making dangerous small boat journeys to the UK to claim asylum.
They say that their removal is lawful under rules that deems asylum inadmissible if they have made dangerous and unnecessary journeys from a safe third country like France.
Around 130 migrants who entered the UK are currently being detained ready for flights starting next Tuesday although at least 90 have individually lodged legal challenges to their removal.
Migrants due to be flown to Rwanda are likely to be released into the community and could be tagged amid fears they will try to abscond if the Government loses the injunction battle on Friday.
‘Serious concerns about access to fair procedures’
The UNHCR document, submitted to the court, stated it had “serious concerns that asylum seekers transferred from the UK to Rwanda will not have access to fair and efficient procedures for the determination of refugee status, with consequent risks of refoulement.”
Refoulement is the legal term for the forcible return of refugees to a country where they are liable to face persecution.
It warned that the asylum system in Rwanda where the migrants will be expected to claim refuge is “nascent,” having largely dealt with refugees from neighbouring countries such as Burundi.
“In UNHCR’s assessment, there is a serious risk that the burden of processing the asylum claims of new arrivals from the UK could further overstretch the capacity of the Rwandan national asylum system, thereby undermining its ability to provide protection for all those who seek asylum,” it said.
The UNHCR concluded: “The UK-Rwanda arrangement fails to meet the required standards relating to the legality and appropriateness of bilateral or multilateral transfers of asylum-seekers.
“This arrangement, which amongst other concerns seeks to shift responsibility and lacks necessary safeguards, is incompatible with the letter and spirit of the 1951 Convention.
“In UNHCR’s view, the UK-Rwanda arrangement cannot be brought into line with international legal obligations through minor adjustments.
“The serious concerns outlined in the present analysis require urgent and appropriate consideration by the governments of the UK and Rwanda in line with their obligations under well-established and binding norms of international refugee law.”