The Ministry of Defence (MoD) has admitted there have been 49 other data breaches in the past four years, handling relocation applications from Afghans seeking safety in Britain.
Four of the 49 breaches were already publicly known, including a leak exposing a spreadsheet containing details of almost 19,000 people fleeing the Taliban.
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The staggering data breach was revealed last month after the High Court lifted a gagging order.
The breach has been described by the UK's information watchdog as a "one-off occurrence following a failure to [follow] usual checks, rather than reflecting a wider culture of non-compliance".
Lawyers representing Afghans affected by data breaches voiced concerns about poor security with the new figures.
The MoD refused to provide any details of the nature of each breach, but previous incidents have revealed email addresses and other personal details to third parties.
Adnan Malik, Head of Data Protection at Barings Law, which represents hundreds of Afghans affected by the biggest of the breaches in February 2022, called the breaches "a series of catastrophic failings".
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Details of more than 100 Britons were involved in the data leak | GETTYHe said: "What began as an isolated incident, which the Ministry of Defence initially sought to keep from public view, has now escalated into a series of catastrophic failings.
"We urge the Ministry of Defence to be fully transparent with both those affected and the wider public. Victims should not be forced to learn the truth through legal action or news reports."
The Afghan Relocations and Assistance Policy (ARAP) was set up in April 2021 to help people who feared their lives were at risk because they had worked with British armed forces in Afghanistan.
It allowed people to apply for resettlement eligibility and for their family members in the UK, with it closing in July this year.
British nationals and Afghan evacuees disembark a flight from Afghanistan at RAF Brize Norton on August 26, 2021 | GETTYThe scheme has been scrapped by revelations about poor data security, with many lives of Afghans who worked with British forces potentially being put at risk.
Defence Secretary John Healey previously offered a "sincere apology" on behalf of the British Government for the data breach in a statement following the initial data breach.
He told the Commons the spreadsheet contained "names and contact details of applicants and, in some instances, information relating to applicants' family members, and in a small number of cases, the names of members of Parliament, senior military officers and Government officials were noted as supporting the application".
The breach affected between 80,000 and 100,000 people, including the estimated number of family members of the ARAP applicants.
The breach resulted in the previous Government's creation of a secret Afghan relocation scheme - the Afghanistan Response Route - in April 2024.
The scheme is understood to have cost around £400million so far, with a projected cost once completed of around £850million.
Millions more are expected to be paid in legal costs and compensation.
Thousands of Afghans are poised to sue the MoD as a result of the data leak.