Kenner City Councilman Keith Conley will resign from his post and become Mayor Mike Yenni’s chief operating officer when Yenni becomes Jefferson Parish president next month, officials said Tuesday.

Conley, 52, will be the second-highest-ranking official in the parish’s administration after Yenni, 39, is sworn in Jan. 6.

The Kenner City Council will appoint an interim replacement for Conley until an election can be held to choose a permanent successor.

Conley, who is about halfway into his second year as an at-large member of the council, will replace Jacques Molaison, Jefferson’s COO since May.

Before he was elected to the council, Conley was Kenner’s city attorney for seven years beginning in 2007, first under Mayor Ed Muniz and later following Yenni’s election in 2010.

Yenni has frequently credited Conley for helping draw up the $37 million “Kenner 2030” beautification and infrastructure plan for the city as well as for assisting in efforts to redevelop the Laketown and Rivertown sections.

“Keith offers instinctive wisdom and advice (and) is good at bringing people with opposing views to common ground,” Yenni said Tuesday. “His decision process is deliberate, and he is dedicated to every task.”

Conley said it was difficult to leave the City Council but that his new job offers a chance to serve “the entire parish and not just Kenner.”

“I (also) believe in Mike Yenni, his vision, his dedication to public service and his unique ability to motivate those around him,” said Conley, whose resignation will take effect Jan. 6.

“I can easily see how Mike’s energy, enthusiasm and experience in government will accelerate Jefferson’s development and catapult our parish to the top of many categories,” he said.

Before joining Kenner’s municipal government, Conley worked for a time as the city’s clerk of court. The Loyola Law School graduate also served as a clerk in the 24th Judicial District Court in Gretna and logged more than two decades with the Jefferson Parish Sheriff’s Office.

Conley was one of Yenni’s most vocal and visible supporters before the mayor defeated four opponents Oct. 24 to win the right to succeed John Young as parish president. Yenni later appointed Conley to his transition team.

There was no official word Tuesday on who will be tapped to fill Conley’s at-large seat on an interim basis. But Conley and local businessman Brian Brennan have been meeting with council members about the possibility of Brennan’s becoming Conley’s interim replacement, Kenner government insiders said.

Brennan was part of a transition team Yenni assembled after he was first elected as Kenner’s mayor. He ran for one of the Kenner council’s district seats in 2010, losing to Kent Denapolis, who four years later withdrew from the runoff election that put Conley in the at-large seat.

Conley will be joining an administration that will include several officials with ties to Kenner’s municipal government as well as some holdovers from Young’s staff.