"The three police forces are looking at transformational outsourcing offered as part of a framework that runs for 10 years. They are doing a business case and so are clearly examining all the options that they have for saving £73m in costs."

She added: "These types of long-term transformational deals require strong management and buyers have options. They can reduce risks by having exit clauses and termination strategies. Different types of pricing can also be negotiated. At Lincolnshire Police G4S has underwritten the £20m or so savings."