Mr Amaechi, over the weekend, in two separate audios, was reported to have spoken ill of the government of which he serves.
Sani said those who will carry out the campaign may be assaulted while trying to do their assignment.
Despite his acclaimed stance, Obasanjo has publicly endorsed Atiku Abubakar, presidential candidate of the PDP to battle it out with the president.
Although the two firms have denied cronies of the president bought it shares, Atiku has continued to insist that a probe on the matter should be carried out.
Buhari had earlier accused Atiku of sponsoring fake news against himself and his administration.
Messrs Buhari and Abubakar are presidential candidates of the two major political parties who are participating in next year's election.
Bakare said Buhari did not assemble the best cabinet that will turn things around unlike those of his predecessors.
Messer Abubakar and Buhari are major presidential candidates for the next year's election.
Sani said the agreement must be signed in the presence of well known religious and traditional office holders.
Mr Mbaka, a Catholic priest, made the call on Tuesday in a new year message to Nigerians.