KiwiRail originally considered a kitset approach when buying hundreds of rail wagons from China.
Documents released to Radio New Zealand after an investigation by the Ombudsman show that KiwiRail identified the possibility of importing and assembling wagons in New Zealand during the tender process for 300 flat-top freight wagons in 2010.
In a letter, the company told three Government ministers it would pursue the option only if it closed the gap significantly, in terms of cost.
Ultimately, 500 complete wagons were bought in two orders from China. The wagons have had commissioning problems.
KiwiRail chief executive Jim Quinn says having a manufacturer accountable was better and cheaper for the company.
Dunedin South MP Clare Curran says the loss of 44 jobs at KiwiRail's Hillside workshops could have been avoided if some of the assembly had been done in New Zealand.