The party's constitution required a special general meeting after every election, at which the leadership was always considered. In the past it had been a formality because both co-leaders had committed to staying on.
"But the reality is that both are retiring, we need a succession plan in place to ensure we are well prepared and we are getting on with that."
Party president Pem Bird earlier said the expectation was for a change by the end of the year. However, it was up to the executive to call it.
Mr Flavell said if he was the leader he would like a ministerial post. "It probably fits one to the other."
Another option is for Mr Flavell to stay out of a ministerial position and instead focus on the leadership.
It would allow him to speak out more openly against National policies than he could as a minister, a role bound by confidentiality requirements.
The party will meet its members over the next week to gauge views on a coalition agreement before deciding whether to sign up with National.