National leader John Key has revealed a conversation with former Labour prime minister David Lange was instrumental in his decision to rule out ACT founder Roger Douglas from a future National-led cabinet.
Sir Roger implemented sweeping economic reforms as finance minister under Mr Lange's fourth Labour government in the 1980s.
He is now ACT's third ranked candidate and on current polling stands a strong chance of making it back into Parliament.
ACT has pledged to support a National-led government but Mr Key has shut the door on a cabinet post for Sir Roger whom he says has "radical right-wing views".
Mr Key said he met the now-deceased Mr Lange years ago at a dinner function, before he entered Parliament.
When he told Mr Lange he was keen to get into politics Mr Lange tried to discourage him.
"His face changed and he became really negative and he advised me not to do it. He said it would be the biggest mistake of my life," he said.
"He certainly regretted it, is my sense."
Mr Key said he felt that was because of the Douglas-led changes made under his watch.
"That's one of the reasons I ruled Roger Douglas out, because in the end you've got to feel comfortable with what you are doing and if you don't, you actually have to front up to the New Zealand public," he said.
"Unless you believe in the agenda you've got then you'll never feel comfortable with it and you'll never be sincere and that was the reason I took the call because I can't lead a government I don't believe in."
