Nicola Willis rejects supermarkets' criticism, pointing to 'vested interests'

National's finance spokesperson has pushed back against criticisms from supermarkets and businesses of the party's policy to break up Foodstuffs.

Nicola Willis was responding to the latest GDP figures - up 0.2 percent in the June quarter - but spent just as much time defending National's supermarkets policy.

She stood alongside leader Christopher Luxon on Wednesday to announce the plan to break up Foodstuffs - splitting the Pak'nSave and New World brands - if a Commerce Commission review agreed that was the best course.

Supermarkets and business groups have warned however the idea could have a chilling effect on investment.

Foodstuffs' North Island chair Dean Waddell said the company was "gutted and concerned" and - in direct conflict with its goals - the proposal would drive prices higher.

But Willis said that claim was "extraordinary".