ACT Leader David Seymour is calling on National to rule out working with the Greens after the election, saying the Greens' stance on welfare is "communism without the stealth".
The Greens announced a families policy on Sunday that increases benefits by 20 percent and removes financial sanctions, while raising the top income tax rate to 40 percent from 33 percent.
The Greens will also raise the minimum wage to $17.75 an hour next year and increase it to 66 percent of the average wage by 2020.
Mr Seymour said the Greens had embraced envy politics and endorsed dependency.
"By removing drug test and job search obligations tied to benefits, the Greens suggest it's OK for people to live off the taxpayer with no strings attached.
"If you stay at home and smoke drugs all day you get a pay rise. If you get up and go to work you get a tax hike," he said.
ACT is a support partner of National in the current Government. It has one seat in Parliament and about 1 percent support in polls.
Mr Seymour says National "needs to condemn this, as a supposedly centre-right party".
The benefit is meant to be a safety net, not a lifestyle, he said.
"You can't solve poverty by throwing money at it," he said.
Under ACT's tax plan, no-one would have to pay more than a 25 percent tax rate, Mr Seymour said.