The cost to replace the potential new flag waving atop the Auckland Harbour Bridge which is the wrong colour will reach nearly $4000, officials have confirmed.

Hoisted alongside the present flag, the huge Kyle Lockwood fern and Southern Cross design contains the wrong shade of blue and will go within the next seven days.

"The fabric weight and printing technique used to produce the alternative flag flying on the Auckland Harbour Bridge has resulted in a lighter blue than the silver fern flag eligible voters will consider in the final referendum," a NZ flag consideration project spokeswoman said.

"The NZ Transport Agency is currently producing one in a different fabric to resolve this. It is being produced as quickly as possible and will be installed next week."


The spokesman said the replacement will cost "less than $4000" and include the price of a back-up flag "in reserve for weather damage", in line with Transport Agency protocols.

"The bridge flag is large and for safety reasons it needs to withstand all types of weather conditions, that can be extreme at times," she said.

"If the flag deteriorates and rips, or breaks and falls on the traffic below, it would be a significant safety hazard."

None of the other 300 flags around the country are the wrong colour, the spokeswoman said.