KiwiRail announced late on Friday that they had reached a short list of four potential suppliers to build trains for the Auckland Rail Network, following an expression of interest process in May.

The decision has enraged the Rail and Maritime Transport Union Rail.

General Secretary Wayne Butson says workers are gutted that the trains are not being built in New Zealand, despite the capacity existing at Hillside and Woburn workshops.

Butson says both facilities provide a comprehensive economic case backing a local build.