Campaign groups have criticised the Home Office after it refused to release details of which countries are deemed a “risk” in an algorithm that filters UK visa applications.

Campaigners for immigrants’ rights were sent a fully redacted list of nations in different categories of “risk”, which were entirely blacked out, on a Home Office response to their legal challenge over the artificial intelligence programme.

In defence of its use of the AI system a Home Office spokesperson said the programme fully complied with equality legislation.

Foxglove, an advocacy group promoting justice in the new technology sector, is supporting the case brought by the Joint Council for the Welfare of Immigrants (JCWI) to force the Home Office to explain on what basis the algorithm “streams” visa applicants.

Responding to a letter from the JCWI as part of a pre-legal action move, the Home Office admitted that it decides who gets into the UK on the visa system through nationality.

But Foxglove said the Home Office refused to publish its list of what the campaign group labelled “the undesirable” nations in its correspondence to them and the JCWI.

“The list provided to us is entirely redacted,” said Cori Crider, a director at Foxglove.

“Boris Johnson claims he wants ‘people of talent’ coming into Britain, but the Home Office’s secret list of undesirable countries sure makes it look like its visa algorithm is a convenient way of keeping people of colour out.”

Chai Patel, JCWI’s legal policy director, added: “We know from the independent chief inspector of borders and immigration that Home Office enforcement activity is primarily targeted at only a few nationalities that are easy to remove, so it is likely that information about ‘high risk’ nationalities will be biased by definition.

“We also know that Home Office databases are full of errors, and decisions are hugely flawed with 52% of appeals against Home Office decision-making being ruled incorrect. Algorithms, and streaming tools are only ever as good as the data that goes into them: if discriminatory data and decisions go in, then that is what you will get out.”

But the Home Office defended the use of the AI tool, stressing that the final decision on entry to the UK was made by immigration officers.

A Home Office spokesperson said: “As the public would expect, we have always used processes that enable UK Visas and Immigration to allocate its high volume of cases in an efficient way.

“The streaming tool, first developed in 2015, attributes a risk rating to an application based on a number of criteria, including nationality, and this rating is used to allocate work to caseworkers, not decide the application. Every application is decided by an entry clearance officer.

“The tool complies fully with the relevant legislation under the Equality Act 2010.”

The Home Office spokesperson added that UK Visas and Immigration received more than 3.3 million visa applications in the year ending June 2019, of which just under 2.9 million were granted.

“The service standard for processing a visit visa is 15 working days. Last year we processed 97% within this target. The UK welcomes genuine visitors. Over 2.4 million visitor visas were granted, for leisure, study or business, an increase of 8% in the past year.”

In its legal action the JCWI is demanding all the technical details that drive the streaming tool be revealed, along with further information such as case-working targets in each of the three categories, and if there have been any complaints about the deployment of the algorithm.

The campaign group argues that the use of the streaming tool is a more modern version of a visa entry system ruled unlawful by the House of Lords in 2005.

It concerned Roma applicants who were said to have been treated with more suspicion and subjected to more intense and intrusive questioning than non-Roma applicants. The Lords concluded that the “stereotyping of Roma as being less likely to be genuine visitors” to the UK was unlawful.