Croydon’s libraries will be handed over to one of five shortlisted organisations.
Along with Wandsworth Council, the local authority has been working to find a partner to run its library service.
The council stated the winning bidder would provide “better value for money for tax payers”.
But campaigners fear the handover will lead to library closures and poorer services.
A Save Croydon Libraries group has been set up to try and ensure services remain the same.
The five bidders are a mix of local authorities and commercial companies, the council said.
Croydon’s cabinet member for customer services, culture and sport Cllr Sara Bashford said: “Over the years Croydon has seen substantial cost savings and service improvements through contracting arrangements such as these and our intention is to see this repeated through this exercise.
“These organisations have shown that they potentially have the vision, expertise and financial backing to deliver modern, efficient and effective library services.
“Closure is not an option for us. Our central library is the third busiest in the country, and last year we consulted widely on the future of all of our branches. We got the message loud and clear that these are important community facilities that must be kept open as a matter of priority.”
Both authorities have said all core services should remain free of charge, buildings would remain in public ownership and councillors would continue to control opening times.