An economist says removing GST from fruit and vegetables can become very complicated in practice.

National claims it is part of Labour's election tax policy, but Prime Minister Chris Hipkins is refusing to either confirm or deny it.

Nicola Willis says she has been leaked the information.

ASB Senior Economist Mark Smith told Francesca Rudkin the extra administration to do this comes at a cost.

He says ideally you would take a targeted approach, but that is hard to do.

Smith says other countries ask people show their income to get the discount, but it comes with problems.

LISTEN ABOVE

• National's Nicola Willis: Let's face it, Labour's been leaking like a sieve
• Heather du Plessis-Allan: Labour haven't denied plans to drop GST on fruit and vegetables