ACT Party leader Rodney Hide says he under-estimated the resilience of his former deputy Heather Roy, who was dumped last week.
The party has been in turmoil following Mrs Roy's demotion and the leaking of a dossier revealing a dysfunctional relationship between her and Mr Hide.
Mrs Roy returned to Parliament this week.
She and Mr Hide presented a united front on Thursday, walking into Parliament side by side saying their differences were behind them.
At a caucus meeting, Mrs Roy apologised for the damage caused by the leak and said she accepts Mr Hide did not act to undermine her. He also apologised for causing her any distress.
Mr Hide says it is a shock for anyone to be demoted and it has taken other MPs longer to recover.
He says Mrs Roy is a lot tougher than he realised.