He said multimillion-dollar properties in the Auckland suburb of Remuera, or Wellington's Oriental Bay, would be exempt from a capital gains tax.
"But those in the Hawke's Bay with a few sheep and some cows will be hit. Labour claims this is about fairness, but how's that fair?"
Robertson said the Government was seeking advice on the report and no final decisions on a Capital Gains Tax have been made.
He said any capital gains made up until the point a CGT is introduced will be protected, so the tax, if adopted, will apply to financial gain made on a property only after April 1, 2021.
The recommendation to not exempt properties over 4500 square metres is based on existing laws around what is considered a "main home" when selling properties under the brightline test, a tax introduced by National in 2015.
A capital gains tax only affects a property when it is sold.