Auckland Transport fears lower government subsidies for local roads will hamper connections with a well-funded state highway network on which traffic has eased.
Its concern comes after a month of falling traffic volumes across the network - including on the Auckland Harbour Bridge.
The transport agency has reported a 3.4 per cent decline in all traffic across the network for last month against April last year, and a 2 per cent decrease in heavy vehicles.
It reported a 4 per cent reduction of traffic on the harbour bridge and on the Ngauranga intersection of state highways outside Wellington.
Although the figures have been seized on by the Green Party to question the Government's priorities in increasing highway spending while cutting other categories, Transport Minister Steven Joyce insists freight traffic is on a long-term growth path.
"There's no doubt the graph has flattened but nobody's arguing we've removed congestion on the Auckland motorway system," he told the Herald yesterday.
"I think they are still expecting us to do Waterview," he said in reference to a $1.7 billion package of motorway projects.
Labour also says it would put plans for a $1.65 billion highway between Puhoi and Wellsford, north of Auckland, on hold indefinitely if elected.
Mr Joyce agreed flat economic conditions and high fuel prices were among potential causes for the declining traffic, but said it was likely to pick up as the economy began to recover.
He also denied a claim by Auckland Transport that the Government was squeezing funding for local roads beyond acceptable levels, saying it had simply produced a range within which the Transport Agency would allocate funds for the three years from 2012/2013.
"The renewal and maintenance budgets are proposed to be held at close to current levels to drive further efficiencies in delivery," he said.
"This approach is also being taken with the state highway network. In the case of Auckland there should also be efficiencies from the bringing together of the seven previously separate local roading operations."
Auckland Transport, which is preparing submissions on a draft Government transport policy directive for 2012 to 2015, is upset proposed national spending on new or improved local roading is being cut to a range of $390 million to $550 million from $450 million to $750 million for 2009-2012.
A staff report to its board said that would reduce its ability to meet key goals of its statement of intent, especially to "deliver a properly connected arterial road network that is integrated with the state highway network and moves people and goods efficiently and safely".
It also said an indicated cut in maintenance funding would put severe pressure on service levels for Auckland's existing roads.
Mr Joyce said a mid-point in the new range for new or improved local roads, of $473 million, would be 4 per cent higher than actual spending of $453 million for 2009-12.
He said the figure was at the lower end because government subsidies depended on programmes done by local councils, which stopped spending on roads after development levies dried up in the global financial crisis.
The Government is proposing to spend between $2.7 billion and $3.6 billion in the three-year period on new highways, compared with $3.1 billion between 2009 and 2012.
*Proposed range of Government subsidies on new and improved local roads from 2012 to 2015: $390 million to $550 million.
*Proposed range of government direct spending on new and improved state highways from 2012 to 2015: $2.7 billion to $3.6 billion.