Auditor-General Lyn Provost is holding off commenting on the $2.4 billion city rail link until details of the project appear in a new 10-year budget for the Super City.
Ms Provost appeared before Auckland Council's audit and risk committee at the Town Hall today where she was quizzed on the rail link by councillor Cameron Brewer.
The Orakei councillor asked her about the costings and funding of the rail project, which is regarded as the city's top priority by Mayor Len Brown and most councillors.
Once details emerged, Ms Provost said the financial watchdog would look at the assumptions made, funding sources, whether the strategy hangs together and whether the numbers add up, to form a judgment on the consultation document for the budget and the final budget itself.
Mr Brown wants to make a start on the rail link in 2016, but has still to put together a detailed funding package in the budget, which includes $7.5 billion of proposed cuts in capital spending and running costs, including less money for parks, swimming pools and libraries.
Auckland Transport has recently sliced about $460 million off the $2.86 billion underground rail project by scrapping its deepest station and pushing back the need for new trains beyond the new 10-year budget.
Mr Brewer said that in February Ms Provost said her office would require a lot more certainty and information around the costings and funding of the rail link before she signed off an audit opinion for the 10-year budget.
He said at the last 10-year plan in 2012, Ms Provost raised a number of issues around the "significant level of uncertainty" with the Government's half share of the cost and locking down "alternative funding sources".
In 2012, Ms Provost said: "The main risks to the city rail loop project are that central Government will not agree to provide direct funding nor enable the council to access alternative funding sources."
Since then, the Government has agreed to fund half the cost with a start date of 2020.