Worcestershire county council has confirmed that a laptop belonging to IT supplier Serco Solutions containing sensitive information on more than 16,000 staff has been stolen.

The laptop, which contained names, addresses, national insurance and bank account details was stolen in a street robbery last week. A council spokesperson confirmed that the data security breach “potentially affected a little over 16,000 staff”.

The council was “not completely sure of the level of encryption” on the stolen laptop, “but our understanding is there was security on the machine”, she said.

Serco had the staff data because it is working on a new payroll system for the council, the spokesperson said, adding “That doesn’t explain why they were keeping it on the laptop.”

Worcestershire council corporate services director Patrick Birch said “We have sought guidance from the Information Commission and we are continuing to work with staff, senior managers and unions to give concerned staff our full support and guidance.”

The council has written to all the potentially affected staff and has set up a helpline.

Serco was unavailable for comment.