The Labour Party says ACT's newly announced policy of cutting the company tax rate to 12.5 percent does not stack up.
ACT is proposing to boost economic growth by a third by bringing the company tax rate down to 12.5 percent, from 28 percent, over five years.
The party's leader Jamie Whyte said the tax cut would increase investment and jobs which would lead to wage rises.
He said the tax cut would be offset by getting rid of $1.5 billion of corporate welfare and carbon trading.
However Labour Party leader David Cunliffe said ACT's numbers were way out and would just transfer funds to the rich.
He said halving the company tax rate would amount to more than $1 billion shortfall in revenue. ACT will release the full costings of its policy this week