Auckland mayor Mr Len Brown told the governing board meeting that a 2015-16 start for the project was considered "too much of a stretch by the auditor-general," Ms Lyn Provost. The council had assumed that the government would begin funding for the main works of the project in 2015, when it committed to a 2020 start date for construction, although Brown hopes to start work earlier.

"The auditor-general is looking for greater clarity and more reasonableness around the timing in bringing the government to the table and getting their assurance around their commitment to funding," Brown says. "I am confident we can come to an agreement in the next 12-18 months and negotiate an earlier start date."

The council is expects to proceed and fully fund enablement works in late 2015 or early 2016, which is estimated to cost $NZ 260m along with land acquisition for $NZ 120m. Preparatory work involves digging cut and cover tunnels from Britomart to Wyndham Street via Albert Street to make way for a major redevelopment of the Downtown Shopping Centre, which is located on the CRL route.

New Zealand's government said in July that it would fund up to half of the project if the start date was pushed back until 2020. Prime minister Mr John Key said that construction could be brought forward if employment levels in the city centre increase by 25% and annual commuter rail trips hit 20 million a year.

Brown initially baulked at the suggestion, but suggested delaying the start date by two years earlier this month after Provost said the 2015-16 was overly optimistic. Provost also said her office would refuse to sign off the council's 10-year budget until funding was guaranteed.

With a 2018-19 start the project would be completed in 2023.