Aucklanders could pay an extra $4 to $6 every time they go to the petrol pump under a plan to help fund Labour's rail link to the airport, party leader Jacinda Ardern says.
Labour has promised to build a light rail line between Auckland city and the airport within a decade.
To help fund the project, the party would allow Auckland Council to collect a regional fuel tax, saying councils have been asking for these kind of revenue raising tools.
Previous estimates by council-backed reports had thought it possible to raise $160 million from a fuel tax, she told Newshub on Tuesday morning
"The rough range we've looked at for the fuel tax is around 10 cents per litre," she said.
"So depending on someone's fuel usage, we are looking at around $4 to $6, perhaps, every time they fill up."
Over the weekend, National's campaign boss Steven Joyce criticised the tax, saying it was Labour policy back in 2007 and it had been rejected by voters many times.
He said 10 cents a litre would be just the start of what Labour would charge and would have a real impact on the cost of living for Aucklanders.
Under Labour's plan, the line would link Wynyard Quarter in the city to Mt Roskill within four years, before extending from Mt Roskill to the airport within a decade.
A west Auckland connection would also be built within 10 years, followed by a line from the city to the North Shore.