According to Mr Mahama, the president is not matching his promise with delivery when it comes to corruption.
He made this known on Tuesday while addressing delegates of the National Democratic Congress (NDC) at Axim in the Evalue-Gwira Constituency of the Western Region.
The immediate past president is on a five-day campaign tour of the Western Region.
He told the delegates that President Akufo-Addo has consistently cleared his appointees of corruption allegations, pointing out that that is at variance with his promises while in opposition.
Already, there have been criticisms against the president over his fight against the canker.
Former President Mahama also spoke on issues affecting fishermen.
He said the rising cost of pre-mix fuel and the astronomical prices of outboard motors are taking a toll on the sector.
He therefore called on all members of the NDC to unite and work hard for victory in 2020 in order to address these challenges.
Mr Mahama is also promising to work hard to provide jobs and reduce the high cost of living when elected in the next presidential election.