Northland MP Winston Peters says recurring power cuts in the region raise the question of whether it is getting enough investment in infrastructure.
30,000 properties from Cape Reinga to just north of Whangarei were without power for several hours yesterday.
The blackout left business leaders fuming.
New Zealand First leader Mr Peters, who has been the MP for the region since March, said it wasn't an isolated incident.
He said the economic cost of the failure at the substation was phenomenal, and something the region could ill-afford.
Mr Peters said he suspected there had been a lack of investment in Northland, and wanted to know if that was something the government had been seriously monitoring.