Major flaws in a huge Home Office immigration database have resulted in more than 76,000 people being listed with incorrect names, photographs or immigration status.

Leaked internal documents reveal the scale of the database fiasco at the Home Office, which has recently been criticised for delays in immigration application processing, long queues at borders and the distribution of incorrect identity cards.

The Home Office has been relatively silent about the database failures, referring vaguely to them as “IT issues”. Ministers have denied there is a “systemic” problem with Atlas, the tool used by border officials and immigration officers which operates off the flawed database.

Documents seen by the Guardian, however, shed light on the department’s attempts to remedy a widespread problem that is causing people’s data to be mixed up, often with that of complete strangers.

The problem, which involves “merged identities”, where two or more people have biographical and biometric details linked incorrectly, is leaving people unable to prove their rights to work, rent housing or access free NHS treatment.

Government sources confirmed that an investigation was under way by the Information Commissioner’s Office, which is considering whether the failure represents data breaches.

‘Echoes of Windrush’

In January, the Home Office knowingly exacerbated the problem when, after a year of planning, it changed the way the database linked individuals’ records in order to improve their accuracy for several million people.

A document seen by the Guardian highlights a “small but important downside […] a few thousand people in the database who (typically due to human error) had other people’s passport details recorded on their records. The trade-off here was deemed by the business [the Home Office] to be worth it, hence the approval to proceed.”

Information in the leaked documents suggests that data relating to at least 76,000 people has been affected.

David Neal, the recently sacked borders inspector, said the Guardian’s revelations appeared to “confirm my previous fears that the Home Office’s data is inexcusably awful”. He has called for an immediate independent investigation.

“The fact that the Home Office appears to have priced in these errors should be a matter of deep concern,” he said. “It echoes the Windrush scandal, which is still affecting the department to this day.”

The database at the heart of the failures is known as the Person Centric Data Platform (PCDP) and stores a migrant’s interactions with the UK immigration systems over time, including visa applications, identity documents, and biometric information. It stores the records of 177 million people and is part of a Home Office project to fully digitise visa and immigration systems that has cost more than £400m since 2014.

PCDP records feed into Atlas, a Home Office computer system used by caseworkers and Border Force officials to view information on migrants, as well as a number of online systems used by people to prove their immigration status and rights.

The issue of merged identities means Border Force officials looking up details using one person’s passport number may get the name, photograph or immigration status of someone completely different on their screen. Meanwhile, people logging on to a Home Office portal to prove their right to work or rent to employers and landlords may be shown the names and photographs of other people instead, putting potential jobs and housing in jeopardy.

‘My life is no longer my own’

The Guardian has spoken to several individuals affected, and lawyers and NGOs have raised concerns about many more.

Jorge Gómez, a rugby player who represented his national team in Nicaragua, was recognised as a refugee in December 2022. However, despite calling the Home Office more than 100 times, he said, he had been unable to prove his right to work to employers. “It says I’m not eligible to work even though I am,” he said. “I feel that the Home Office has damaged my life and my mental health.”

Another refugee repeatedly saw the photo ID of a stranger when she logged on to her online immigration account. A different woman, who is on the EU settlement scheme, was unable to take up a job offer due to digital mistakes in her migration status.

One woman who found details on her online immigration account swapped with another person’s said: “We are hostages to this ridiculous system. We are left trying to prove who we are. My life is no longer my own. We are being made to feel like failures but it is the system that has failed us.”

Andreea Dumitrache, of the3million, a campaign group for EU citizens living in the UK, said: “This government is enforcing and expanding a deeply flawed online-only immigration system. The Home Office tampers with our status and we’re the ones suffering the consequences.

“Imagine waking up one day and it’s your word against a computer system – and your future depends on it. We need an immigration system which is based on fairness and compassion, not hostile environment policies which embed immigration control into every aspect of life.”

Such errors are described in the internal Home Office documents as “reputationally damaging for the Home Office and worrying for affected customers when presented with a stranger’s facial image and personal details”.

The documents call the problem of merged identities a “longstanding issue”, and reveal that a team has been set up to manage the fallout. That raises questions about whether ministers have been transparent about the problem.

In February, the Home Office minister Tom Pursglove played down the issue, telling parliament that “no systemic issues” had been identified with Atlas. However, the documents suggest the issues are rooted in its flawed data system.

Last week the i newspaper reported that issues with Atlas had left Home Office asylum caseworkers “sobbing” as the problems were causing them to miss performance targets and financial incentives.

Officials working on immigration applications are unable to work on any cases where there is an issue with merged identities in case further problems are caused.

Internal documents reveal the Home Office created an automated tool designed to flag potential merged identities. It has so far found more than 38,000 issues, each of which will affect at least two people.

A Home Office spokesperson said the issues were estimated to have affected 0.02% of individuals on the database.

“Steps have been taken to mitigate any risks for people and address the issues as quickly as possible,” they said.

A spokesperson for the Information Commissioner’s Office said: “People’s trust in a system relies on them being sure their information is being kept securely and accurately. The ICO is investigating this issue, following a report to us by the Home Office.”