David Parker says anyone disappointed with his party's tax policy is free to vote for someone else.
Labour on Wednesday announced if re-elected, it would not make big changes to the tax system - the only significant change being a new top tax rate of 39 percent on income earned over $180,000.
The party said that would only affect 2 percent of earners but raise $550 million a year.
The policy has been slammed by the Opposition, saying it would punish people for succeeding and hardly make a dent in the Government's debt, which is at a record high thanks to the COVID-19 pandemic.
"It doesn't raise much money," National MP Simon Bridges told The AM Show on Friday.
"It doesn't hit the truly wealthy, because the corporate and trust rates are much lower, so they'll be able to play around with that... I strongly dislike it and it's simply for this reason - it sends a signal to young New Zealanders if you go to varsity, if you do well, if you're gonna be out there earning good money in due course, that we don't value that. I think society is lesser for that."
Statistics NZ figures show there were 49,130 Kiwis who earned more than $180,000 in the 2019 calendar year. They brought in about $13.8 billion between them - an average of about $280,000. A person on that amount would be paying an extra $115 a week in tax, out of a weekly gross pay of $5384.
The median income is about $52,800 a year - $1016 a week.
"I think $180,000 is a high income in New Zealand," Parker, appearing with Bridges on The AM Show, said.
"You're pretty well-off if you're getting $180,000 - you're in the top 2 percent of income earners."
The policy has also been criticised by Labour's partners on the left, the Greens, who want more tax brackets and wealth taxes. Co-leader James Shaw said Labour's plan fails to address "the growing wealth gap and inequality in Aotearoa" and won't be near enough to help pay for the COVID response and recovery.
"If you're in the top 6 percent and can't afford being taxed slightly more then try not eating avo on toast, growing a vege garden, budgeting," Green candidate Luke Wijohn posted on Twitter, mocking advice commonly given to the poor by wealthier people.
He pointed out New Zealand's top tax rates under both the Greens' plan and Labour's would remain "lower than most of the 'developed' world".
Finance Minister Grant Robertson said Labour would not entertain the Greens' tax policy even if they were needed to form a coalition after the election, while Shaw said he'd walk away from negotiations if Labour didn't consider it.
"We're clear - if you don't like our tax policy, vote for someone else," said Parker.
National has promised to index tax brackets to inflation. They haven't changed since 2010, meaning Kiwis are paying a higher effective tax rate now than they were 10 years ago, thanks to rising wages.