Labour and the Greens say National's transport spokesman, Maurice Williamson, has slipped up by revealing that his party intends exempting major roads from the provisions of the Resource Management Act (RMA).
Labour's environment spokesman, Trevor Mallard, circulated copies of a report published in the Upper Hutt Leader newspaper which quoted Mr Williamson as saying National would declare "roads of national importance" exempt for the Act although still taking into account environmental issues.
National's environment policy, released last month, says it will set up an Environmental Protection Authority which would carry out "priority consenting" by making decisions on major infrastructure projects within nine months.
But Mr Mallard said Mr Williamson's reported comments went further than that and meant local people would not have any say over proposed developments in their areas.
Greens co-leader Jeanette Fitzsimons said Mr Williamson had revealed National's secret road-building agenda.
"If National gets its hands on this country, New Zealanders can look forward to a road-building frenzy," she said.
"Without the protection of the RMA, communities will get no say about what gets bulldozed for a `road of national significance'."
