Nashville's police and fire unions, increasingly at odds with Mayor David Briley, have paid for four billboards slamming the mayor over recent pay raises for mayor's office employees.

The billboards are in response to a WSMV-TV story this week that highlighted pay raises for 20 of 27 mayor's office staff members at a time when Briley said Metro government would have to "tighten our belts" amid budget revenue strains.

The raises came as the unions have criticized how Metro workers, including police officers and firefighters, did not get cost-of-living pay adjustments in Metro's current budget as originally promised.

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The Nashville Fraternal Order of Police, Nashville Firefighters Association Local 140, and the National Black Police Association paid for the billboards, which are located in different parts of Nashville.

The billboard, featuring an image of the mayor's face, quotes Briley from the recent television report when he said, "People (in the mayor's office) who got the increases ... undertook additional responsibilities."

"We took additional responsibilities ... " the billboard continues.

"Where are our promised increases?" it concludes.

WSMV-TV reported that 10 mayor's office employees received a 3.5 percent increase; seven workers got a 3 percent increase; two workers received a 6 percent increase; and one worker got a 2.5 percent increase.

Each is included in the current 2018-19 fiscal year budget.

That includes a $7,178 pay increase for Briley's Chief Strategy Officer Brian Kelsey, whom the mayor's office has said is taking on more duties following the upcoming departure of top aide Rich Riebeling, the mayor's chief operating officer. Riebeling is set to leave on Oct. 16.

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The mayor's office has rejected the premise of the television report, arguing that 71 percent of employees across Metro can in fact expect some type of pay increase this year as part of the budget despite the cost-of-living adjustment not happening.

According to the mayor's office, 6,813 out of 9,552 Metro employees (excluding school employees) are eligible for either open-range or step increases — the two other ways employee pay increases are provided.

Press Secretary Judith Byrd said the mayor's office has lost 13 staff members during the transition from former Mayor Megan Barry, who resigned in March, and has replaced only seven of them. She said mayor's office salaries are down 11 percent as a result.

She said the three employees who received 6 percent pay increases, including Kelsey, had "significant promotions."

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The Metro Council approved the mayor's budget this spring, voting down a property tax increase that would have restored a cost-of-living adjustment for Metro workers.

As part of a budget compromise with the council, the final budget reduced the overall budget of the mayor's office by $300,000, or 6.6 percent.

The Nashville FOP has indicated its ready for a legal battle following District Attorney Glenn Funk's decision Thursday to file charges in the death of Daniel Hambrick, who was shot and killed by police office Andrew Delke during a footchase in June.

But Briley supported Funk's move in a statement, calling it a "necessary step" toward justice for Hambrick.

In addition, the Nashville FOP is currently engaged in a lawsuit with Metro government over the Davidson County Election voted to add a referendum on a community oversight board for police to the November ballot.

Davidson County Circuit Court Judge Kelvin Jones dismissed the FOP's lawsuit last week, but the FOP has appealed to the Tennessee Supreme Court.

Amid a dispute over the cost-of-living adjustment, the Nashville FOP did not endorse Briley during this year's special mayoral election despite him being a heavy favorite to win. The fire union also declined to endorse in the race.

Reach Joey Garrison 615-259-8263, jgarrison@tennessean.com and on Twitter @joeygarrison.