Lungu has been accused by critics of increasingly authoritarian rule and of cracking down on dissent.
Zambian President Edgar Lungu on Sunday requested that Cuba recall its ambassador for allegedly expressing support for a new opposition party.
Cuban ambassador Nelson Pages Vilas reportedly attended the launch of the "Socialist Party" on Saturday in Lusaka and was accused of publicly saying that he supported the party.
"The president has directed that the Cuban ambassador be recalled for behaviour that is unbecoming of a diplomat," presidential spokesman Amos Chanda told reporters.
"The Cuban ambassador attended a party function and announced that he will support the opposition party and said he wished them well."
Lungu has been accused by critics of increasingly authoritarian rule and of cracking down on dissent in Zambia since he narrowly won elections in 2016.
The main opposition UPND party disputes the election result and has filed a motion to impeach the president, but the scheduled vote in parliament last week was delayed.
The motion would likely be easily defeated by lawmakers from the ruling Patriotic Front (PF).
Lungu's spokesman said the request for the Cuban ambassador to be recalled would not affect relations between the two countries.
The Cuban embassy and the Socialist Party were not immediately available to comment.
The Socialist Party's leader was named as Fred M'membe, the former editor of the private Post newspaper that was critical of Lungu's government and which was closed down before the last election.