He said the appointment has eroded the goodwill that came with the recent reshuffle of ministers.
Speaking in an interview on Accra-based Joy News, Mr. Mpianim said Ken Ofori-Atta is the one who led Ghana into its current economic mess.
"Ken Ofori-Atta going is good for the optics. But the person who led us into the financial and economic crisis that we are in, we haven't been here before... there has never been a time when Ghana has not been able to pay its bills and we are not going to start paying them until 2025 this is the same guy who gets us kicked out of the Eurobond market, how can he be an envoy?
"I think Nana (President Akufo-Addo) knows that the international community is not that gullible so you don't send him there. We don't have an economy now, so what is he going to advise on?
"Too many people are walking around the Presidency. Let's remove them. Both governments when they come, remove a minister and he becomes a special adviser at the presidency. We don't want that," he stressed.
Mr. Pianim also said he was unhappy with the resignation of Osei Kyei-Mensah-Bonsu from his role as Majority Leader in Parliament.
Mr Ofori-Atta was relieved of his position as Finance Minister on Wednesday, February 14, and replaced with Mohammed Amin Adam.
Subsequently, the Chief of Staff, Akosua Frema Osei-Opare in a statement dated February 15, announced the new role of the former Finance Minister.