The city jail system's top uniformed official -- under fire for statistics-fudging of inmate violence on his watch -- will leave along with two senior colleagues after just five months in their current posts.

Chief of Department William Clemons, who started in 1985 guarding a Brooklyn jail, will leave Friday and officially retire Dec. 1, the Correction Department said in a statement Tuesday that did not explain his abrupt departure. Mayoral spokesman Phil Walzak said Clemons wasn't ousted; it was a retirement, and Walzak deputy Marti Adams said Martin Murphy, now a chief for custody management, would become acting department chief.

"William Clemons proved himself an able leader as chief of department -- as I expected he would when I appointed him to DOC's highest uniform position," said Correction Commissioner Joseph Ponte.

The other retirements announced Tuesday are two bureau chiefs promoted the same day as Clemons: Joandrea Davis, a guard since 1988, who oversees administration, and Gregory McLaughlin, a guard since 1987, who oversees operations. None of the departing officials could be reached Tuesday.

Correction spokesman Jack Ryan said in a statement that "the commissioner is restructuring the organization" and Davis and McLaughlin "decided to retire instead of moving into a different role."

The Correction Department has been beset by allegations of brutality, corruption, arrests of guards and what federal prosecutors called a "culture of violence."

Clemons was in charge of a Rikers Island jail for juveniles where guards were caught in 2011 leaving out hundreds of fights from reports. An investigation concluded that Clemons had "abdicated all responsibility" on the matter and urged he be demoted -- a conclusion rejected by the Bloomberg-era commissioner at the time -- but Ponte promoted Clemons. Ponte said he hadn't seen the unredacted report, but said he would have promoted him anyway, despite a recommendation against doing so by the city Department of Investigation.

"It was pretty apparent he was asked to leave," said Patrick Ferraiuolo, head of the Correction Captains' Assocation. "It just doesn't make sense that he would be promoted to chief of the department in May and just decide to retire."

Clemons didn't join Ponte this month at a City Council hearing on jail violence, although such chiefs typically accompany their commissioners.

Told Clemons was vacationing, Councilwoman Elizabeth Crowley (D-Queens) charged Clemons lacked "the backbone" to appear. Council Speaker Melissa Mark-Viverito (D-Manhattan) called him "clearly incompetent."

Tuesday, the two council members urged the de Blasio administration "to appoint new leadership that will commit to implementing transparent and humane policies."

With Emily Ngo