Thousands of county council staff are at risk of identity theft after their highly confidential bank and national insurance details were stolen.
A lap top computer containing the personal information of up to 19,000 staff - complete with names and addresses - was taken in a street robbery.
Despite the seriousness of the security breach, in a letter to staff Mike Weaver, the director of financial services at Worcestershire County Council, said he did not want to cause unnecessary concern'. advertisement
He said the laptop was owned and being used by a member of staff employed by the council's IT supplier SERCO who was robbed outside the county several days ago'.
"The personal details include names and addresses," he said.
"Other details relating to national insurance and bank accounts are also held on the computer but are not so easily deciphered.
"Although the theft appears random rather than planned and the computer is password protected, there is nevertheless a risk that this information might be misused."
Adrian Gregson, of UNISON's Worcester branch secretary, said he was very concerned about the theft on behalf of his members.
"We will be raising issues about the council's practices and policies and asking if they will be looking at how this sort of thing is done in the future," he added.
"This has potential to effect a considerable number of staff and we need to ensure that this doesn't happen again.
"In theory not all staff are affected but all have been told."
Patrick Birch, Worcestershire county council's director of corporate services, 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.
"In addition, we are working SERCO Solutions to investigate the matter and help improve their procedures relating to the movement of sensitive data.
"Our first priory in this matter is to protect the confidentiality of our staff and to do everything possible to protect them. We will continue to monitor the situation with the police."
All staff have now been urged to be vigilant and phone a confidential internal hotline which has been set up if they have any suspicions that their personal details are being misused.
The police are monitoring the situation and the incident has also been reported to the Information Commission.