The Council of Trade Unions says National's proposed tax plan would give peanuts to the working and middle classes.
It's crunched the numbers based on IRD and National Party data.
The council says the cut will cost 11 billion dollars over three years, and will mostly benefit top income earners and property investors.
CTU economist Craig Renney told Kate Hawkesby says there are better ways to spend that money.
He says that could be spent on health, education or protecting the poorest workers.
National Party Finance Spokesperson Nicola Willis has rejected the numbers saying they haven't released their entire plan.
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