The Electoral Commission has revealed it has been the subject of a “complex cyber attack” that made copies of electoral registers from August 2021 accessible to hackers.

The attack went undetected for over a year and was only identified in October 2022, the elections watchdog has admitted. The Commission said it has not identified the authors of the attack, adding it is “difficult to accurately predict a figure” for how many people’s data had been affected. 

In a public notice, the Commission admitted the attackers would have been able to access the names and addresses of anyone in the UK who was registered to vote between 2014 and 2022, as well as the names of overseas voters. This would make it one of the largest data breaches to take place in the UK. 

These records are kept by the Electoral Commission for research purposes and conducting checks on political donors. They did not include details of anyone who registered anonymously. 

“We regret that...