A careful and deliberate look at what could be achieved and what efficiencies could be made by the move was needed, he said.
"It increasingly strikes me as dumb to have two regional councils with the same histories and traditions doing much the same stuff."
Otago and Southland were essentially one region as they shared the same climate, history and relationship with Central Otago, and the two regional councils were facing the same issues, such as public transport and increased dairy farming.
Cr Deaker raised the concept when he first stood for the regional council, but believed the "time had now come" to consider the possibility.
"I think the two chief executives and two [chairmen] should sit down and see what could be done."
He acknowledged parochialism could be an issue.
Cr Deaker raised the issue yesterday during the final Otago Regional Council meeting for the year, when the council was discussing the adoption of an economic development policy which suggested it work co-operatively with other Otago councils in the future.
"I feel it's a bit limiting to have Otago in there. I look forward to the day Otago and Southland is one region."
He suggested the proposal to merge the Otago and Southland health boards was another indication of how much the two regions had in common.
"The health people are working up to that; it's time local government do it as well."
Consultation on the health boards' proposed merger closed last week, and a report is to be produced in February.
Chairman Stephen Cairns said he did not disagree with the concept and would not be afraid of discussing it.
"It's got logic."
There were differences between Otago and Southland but he did not believe they were significant.
The health board proposal and the recent Otago and Southland joint bid for the Rugby World Cup showed it could be done, he said.
However, it would take a huge amount of work even before consultation began and would be highly unlikely before next year's local government election.
Environment Southland chairman Stuart Collie could not be contacted for comment.
