Frustration over a blowout of Auckland's City Rail link build cost.

It's asking for another billion dollars, half each from Auckland Council and the Government.

The completion date for stations and supporting rail infrastructure has also been pushed back to November 2025.

Heart of the City Chief Executive, Viv Beck, says it's a big blow for businesses in construction zones.

She says some businesses will have been dealing with the problem for 10 years.

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