Finance Minister Bill English has been forced to defend the Government's intention to allow the Transport Agency borrow large sums of money to pay for new roads.
The Land Transport Management Amendment Bill tabled in Parliament on Tuesday would allow the Transport Agency to borrow to build new roads, subject to the agreement of the Transport and Finance ministers.
It would be a big change from the current system, under which the agency uses money collected from fuel taxes and registration fees to build roads.
At present, the agency can only borrow money to manage cash flow.
During Question Time in Parliament on Wednesday, Green Party co-leader Russel Norman criticised the Government for intending to borrow money for new roads when it argued that it was selling shares in state-owned energy companies to avoid borrowing.
But Mr English dismissed Dr Norman's criticism, saying he can still stop the agency from borrowing money.
Meanwhile, Road Transport Forum chief executive Ken Shirley welcomes the bill, saying the pay-as-you-go system is woefully inadequate.
"That is suitable for minor projects, and it's suitable for renewal and maintenance, but it's not an ideal funding model for long term, major intergenerational projects."
Council for Infrastructure Development chief executive Stephen Selwood says debt funding of new major roads is a logical move.
Mr Selwood told Morning Report on Wednesday that major roads are intergenerational projects and debt could be used to fund the entire budget for the roads of national significance.
Labour Party transport spokesperson Phil Twyford says the Government's fixation on building seven new motorways at a cost of more than $10 billion is behind the proposed change.
"When it comes to road building, this Government's spending is completely out of control. They've basically drained the bank account and now they want access to the credit card."
