The contract is worth approximately £10m a year.
The council calculates that its partnership with Interserve has saved it £6m since 2006.
Interserve is now promising further savings “through an innovative management approach, new service delivery models and changes to service outputs for low-risk service lines”.
Under the contract Interserve looks after building maintenance, security, cleaning, mailroom, reprographics, energy and utilities management, room bookings, porterage and minor and major projects. The contract also includes strategic services such as health and safety, asset and lifecycle management and sustainable development.