Auckland Council chief executive Doug McKay has confirmed an inquiry into Len Brown's spending in the wake of his sex scandal.

The decision was made following inquiries from the New Zealand Herald about whether Mr Brown's affair breached the council's code of conduct and conflict of interest policies.

Mr McKay said today that the Mayor has no council credit card and all invoices and payments from the mayoral budget are checked and approved by the chief of staff.

"I have received an assurance from both the Mayor and his chief of staff that no mayoral office funds were used in relation to the Mayor's relationship with Ms Chuang."

"However I have agreed to independently review this to confirm that is the case."