Atiku Abubakar, a businessman who served as vice president between 1999 and 2007, has portrayed himself as a champion of the private sector. He is the main challenger to President Muhammadu Buhari in a poll to be held on Feb. 16.
Nigeria has at least three exchange rates which the central bank introduced in 2015 at the height of a currency crisis triggered by low oil prices.
"I will rather allow the currency to float so that we can have a realistic single exchange rate that would be stable. That will encourage foreign investors," Abubakar told Reuters. "We will review that policy and ensure we achieve convergence as far as exchange rate policy is concerned," he said.
Abubakar also said he would remove a costly fuel subsidy and identify government enterprises to privatise.
(Additional reporting by Paul Carsten; Editing by Catherine Evans)