The Metropolitan Police has been made aware of “unauthorised access the IT system of one of its suppliers”, the force said.
Scotland Yard is now working with the company to understand if there has been any security breach relating to its data.
The company in question had access to names, ranks, photos, vetting levels and pay numbers for officers and staff, but did not hold personal information such as addresses, phone numbers or financial details, the force said.
A spokesman for the force was unable to say when the breach occurred.
The Met has taken “security measures” as a result.
The matter has been reported to the National Crime Agency – and the Information Commissioner’s Office (ICO) is also aware, the Met said.
It follows an admission by the Police Service of Northern Ireland (PSNI) that personal data on all its serving members was mistakenly published in response to a Freedom of Information (FOI) request.
Details of around 10,000 PSNI officers and staff included the surname and first initial of every employee, their rank or grade, where they are based and the unit they work in.
After the PSNI breach was revealed, Norfolk and Suffolk Police announced the personal data of more than 1,000 people – including crime victims – was included in another FOI response.
On Wednesday, South Yorkshire Police referred itself to the ICO after noticing “a significant and unexplained reduction in data stored on its systems”.
The force said it is now urgently working with experts to recover footage filmed by officers as they attended incidents or engaged with the public and which, in some cases, could be used as evidence in court.
