Sir Roger Douglas says the "socialist" National Party needs a revived version of his 1984 right-hand turn.
Sir Roger led Act's economic policy launch yesterday, where supposed right-wing allies National were firmly lumped in on the left with Labour.
He said Act's policy was "diametrically opposed" to those of the two major parties.
Labour, to which he once belonged, was going to "spend, regulate, hope and pray" its way through the global economic turmoil.
National's response was also "inadequate"; its tax cuts were too small and leader John Key's latest plan to make the New Zealand Superannuation Fund invest more of its money at home was "short-term populism".
Act leader Rodney Hide also criticised Mr Key's plan to direct $800 million of the $2 billion in new money it gets a year to New Zealand assets "as doing nothing to improve New Zealand's economic performance except shift private ownership to the state - something I thought National was against".
"That's why NZ First and the Greens endorse it and, amazingly, Michael Cullen doesn't because it's way too socialist."
Mr Hide said using the fund to buy "Telecom shares and land" directly undermined the fund's purpose, which was to diversify its investments to get the best return for New Zealanders.
Sir Roger said Act's economic plan was to limit Government spending to the rate of population and spending growth - delivering big savings and big tax cuts.
The policy is exactly the same as before the pre-election economic fiscal update and the economic turmoil, the only change a hastily added addendum that puts all his forecasts out by two years.
Sir Roger said the economic crisis simply reinforced the need for this policy, and could not identify any other urgent steps he would take as Finance Minister - the position he held from 1984-88 in the fourth Labour Government. He also could not say what services would have to be cut immediately by bringing the policy into force.
A glaring inconsistency applies to law and order, where Sir Roger said Act would spend up to $1 billion a year on its stringent "three strikes" policy, which would see offenders in prison for 25 years to life after a third serious offence.
Mr Key has ruled out Sir Roger from a Cabinet post or even as a minister outside Cabinet with any National Government.
But Sir Roger said this was just "playing politics", and he would be keen to return to the Cabinet if Act won enough seats to have a strong bargaining position. "I don't think there's any politician who wouldn't [want to be a Cabinet minister]. The vote on November 8 will determine where all the parties sit and therefore the MPs in that party."
Mr Hide said Act could "drag the socialist National Party back on track. As I said to Sir Roger, if you can convince the Labour caucus of the virtues of the free-enterprise economy, I'm sure you can convince National".