Among the cases flagged by ILPA was an NHS nurse who had lived lawfully in Britain for years but had an application to naturalise as a British Citizen denied because of her alleged poor immigration history. A Subject Access Request revealed the Home Office had mixed her up with another Nigerian woman with a slightly similar name and a poor immigration history.

Gracie Bradley, policy and campaigns manager at the human rights group Liberty, told BuzzFeed News the organisation was extremely concerned about the database plans. “The first concern is if there are errors or mistakes. The Home Office is incredibly prone to errors in data processing, it’s an incredibly unreliable data controller.”

She added: “Ultimately the whole logic of the ‘Hostile Environment’ is about locking people out from goods and services so they can’t access healthcare or rental accommodation or work lawfully. So if you are in the UK and don’t have status or can’t prove it, it’s going to be much, much easier to exclude you from these essential services. Some people won’t see that as a problem but we do see that as a problem, especially when it comes to things like accessing healthcare and education. People will be pushed into the arms of abusive landlords and employers.”

Bradley is convinced the policy was deliberately hidden from the public. “During the Data Protection Bill debate we consistently wanted to know why they wanted this exemption. They got the exemption but they never mentioned this project in all the debates. Not once. It’s really disingenuous… I think it’s been deliberately concealed because they were pressed so hard in the data protection debates [and said nothing about it].”

The database will be of particular concern because of the Home Office’s notoriety for poor record keeping. An inspection of a Home Office system of immigration checks for those setting up a bank account revealed that 10% of were wrongly refused accounts because of mistakes in Home Office records. The case of Tapiwa Matukutire, uncovered by BuzzFeed News, also reveals the human cost of poor immigration data sharing. He was arrested and pinned to the floor naked by immigration officers acting on a bad tip off from the DVLA.

Colin Yeo, barrister and editor of the Free Movement immigration law blog, which first flagged the inspection report, said: “There’s been no discussion. They’re creating a population database, and presumably they’ll be expanding it to British passport holders or employers will have two sets of things they have to look at, and there’s been no discussion about it, no discussion in parliament and no white paper.

“Creating a population database is quite a big deal. You’d expect it to be publicly discussed but as far as I know it hasn’t been.”

Yeo said that one of the worrying things about the database was that legal aid has been cut back for most immigration cases, making it very difficult to challenge incorrect records. “We saw with the Windrush cases that once employment has been terminated and there’s no access to legal aid they can’t sort out their problems.” He added: “It’s like being blacklisted but with no way of challenging that. You’d need to contact the Home Office somehow and get them to correct their records and it’s very difficult to do that without legal assistance.”