LABOR faces a union backlash over the delays in the rollout of its National Broadband Network, with the powerful Communications Electrical and Plumbing Union expecting the project to be revised no matter who wins the election and warning of "unacceptable" labour rates to meet cost targets.

The CEPU's Communications Workers Union division - which represents workers involved in the NBN - said there were "fundamental" commercial and operational problems at the heart of the project. The union has also revealed its concerns about delays to the rollout that resulted in NBN Co, which is building the network, last week slashing its targets for the number of homes and businesses that will be passed by fibre by June 30 by as much as 44 per cent. NBN Co has also taken back control of the network construction in the Northern Territory because a lead contractor failed to meet its targets.