National is accusing the Government of wasting taxpayers' money on using Tax Working Group chairman Sir Michael Cullen as a "hired gun," after his contract was extended.
But Cullen – who was also once a Labour Party Finance Minister – rubbished the claim and said he was only staying on to "defend the integrity of the report".
Speaking on The Weekend Collective, Cullen said although people may assume he is biased towards the Labour Party, he is solely focused on the tax working group.
"My job is to defend the integrity of the process and the recommendation and facts which it is based. That is what I am being paid to do."
LISTEN ABOVE AS SIR MICHAEL CULLEN SPEAKS TO THE WEEKEND COLLECTIVE