National is hitting back at criticism of its childcare policy.

Family Boost would give a rebate of up to 75 dollars a week for families earning up to 180-thousand dollars a year.

Social Development Minister Carmel Sepuloni says if that was offered, more people would sign up to childcare which would cause a cost blowout.

But National Party Leader Chris Luxon says that's been factored in.

He told Mike Hosking that he'd welcome an increase in people signing up.

Luxon says that would mean more people would be receiving the support they need.

LISTEN ABOVE