A union fears conditions for civilian staff at Lincolnshire Police could be "eroded" when half transfer to a private company.

In a cost-saving deal thought to be the first of its kind, the police authority is awarding a £200m 10-year outsourcing contract to security firm G4S.

G4S said staff would keep their existing terms and conditions when they transfer on 1 April.

John Gooding, chairman of the Unison branch at Lincolnshire Police, said: "Our members will transfer on their current terms and conditions but as they retire, leave or voluntarily change jobs, then you can dilute the terms and conditions and the working conditions that people do a job under. So gradually it can be eroded - things that we have negotiated over the last 40 years."