A transport lobby group fears the deferral of repairs to a railway line linking Stratford with the main trunk line near Taumarunui could herald future line closures.
The Campaign for Better Transport says the loss of low-use rail lines would have negative environmental and economic effects.
KiwiRail says 8km of railway sleepers damaged in a derailment on the Stratford to Okahukura line last week will not be repaired until next year at the earliest due to low traffic volumes.
KiwiRail says the one return journey a day does not justify expensive repair work, but it will reconsider the issue next year.
The change means Fonterra has no alternative but to send dairy products to northern ports via Manawatu, which it has no problem with.
But the Campaign for Better Transport says this could be the thin end of the wedge for future closures.
KiwiRail faces a financial squeeze and shrinking Government support. It will present a review of its business to the Government later in November, addressing branch line finances and other issues.