The New Zealand Tramways Union is concerned about recent speculation over the potential sale of Citibus.

The Union says that as Citibus is owned by the ratepayers of Dunedin, those ratepayers should be seriously concerned about the loss of the public asset, and the effect it will have on passenger services.

The NZTU are also worried about a potential negative impact on workers' wages and conditions, which may be caused by competitive tendering for the bus service.

Possible new owners of Citibus are NZ Bus, Souter Holdings, Ritchies and Go Bus.