The decision is seen as one that could open the door for other councils to use outsourcing, turning local authorities from providers of public services, to enabling councils that commission others to carry out services.
Dave Prentis, Unison general secretary, said: ??"This is not the way to run council services. There will be no democratic accountability. It is a disgrace that the council has not asked the public, or council workers, what they think.
"Leaving vital services like child protection, home care and support for young people to the vagaries of the market is very dangerous. Services will be sold off to the lowest bidder, starting a race to the bottom. People using local services, and those working to provide them, will pay the price. ??Unison will be working with the local community to challenge these damaging plans."
But Martyn Hart, chairman of the National Outsourcing Association (NOA), said: "There are a number of reasons why councils and other public-sector bodies would wish to outsource - and it's important to note that they are not all linked to cost savings. Outsourcing can help to provide new and different skills, increase the capacity of the workforce, and help to deliver outcomes quicker and more efficiently.
"Indeed, the actual cost savings made can depend on a number of different variables, such as exactly what is being outsourced, what state the services were in before the contracts start, as well as what the council's expectations are.
"Typically, cost savings in the public sector are usually made over a longer period of time, but given a stable set of services at a reasonable pricing level there is the possibility that suppliers can provide cost savings from day one. However, it's worth pointing out that if it's a slick process already, and the public sector organisation is looking to outsource, they may not save as much, they might even consider offering it as a shared service.
"My advice for other councils looking to adopt this model would be to conduct a thorough examination of your core competencies and your ability to perform all the tasks you have. If you find that you not good at a non-core task then outsourcing is an obvious choice.
"Public-sector organisations that are interested in how others have tackled outsourcing, shared services and even in-sourcing should contact the NOA to attend our public sector austerity seminar on Thursday 30 September."