Labour transport spokesman Phil Twyford said the downgrade would mean that section would be "essentially put it on the never-never - which in my view and I think the view of many people is the only rational response given the very low traffic volumes and the extremely challenging topography and geology on that route".
But Transport Agency chief executive Geoff Dangerfield said there was no change to the status of the highway and he apologised "for any confusion caused by an error in a pamphlet".
He said the Warkworth-to-Wellsford section was described as a "possible" road of national significance because the precise route had yet to be determined.
However, despite being told by the agency this year that revenue constraints could delay completion of the roads of national significance including Puhoi to Wellsford by up to three years, Mr Brownlee told Parliament yesterday the road "will be built in the 2015-18 period, unless we get a Labour government that cans it".
Mr Twyford said the Transport Agency explanation for the words on the map was not credible.
"Either they've pre-empted their own announcement of the downgrade or the thinking within the organisation hasn't yet been possibly formalised."
Mr Twyford said it was only a matter of time before it was formalised, because the road was "simply not viable".