Pierre Nkurunziza was bestowed the title over the weekend as critics say he wants to become life president.
“He is our elder, our father, our adviser,” the party’s secretary general Evariste Ndayishimiye said in a video sent to AFP, whose authenticity was confirmed by an official.
Critics have mocked this latest move decrying the cult following around the president.
Burundi is headed for a constitutional referendum in May which would allow Nkurunziza to remain in office until 2034.
Ahead of the exercise, rights groups and the opposition allege authorities have embarked on a massive operation of forced registration of voters including minors, as well as inciting violent action against any opponent of the referendum.
The 54-year-old former rebel leader has ruled Burundi since 2005.