In a statement released Tuesday, the coalition says if voters pass the measure, "it would make it impossible for many city workers to afford health care benefits for their families even after city workers have made concessions in seven of the last nine years, and giving back to the city a total of over three-quarters of a billion dollars."
The labor leaders call Adachi's ballot measure "an attack on working people."
The charter amendment would require city workers to contribute nine or 10 percent of their salaries to their pensions. Right now, most city employees pay 7.5 percent. Some contribute nothing, like Muni operators who say they gave up salary increases in return for the city paying their pension costs.
Adachi's proposed plan would also require city workers to pay 50 percent of their dependants' health care coverage up from the current 25 percent.
Adachi, who is out of town this week, told ABC7 that the city cannot continue paying an unfair portion of workers' pension and welfare costs because of the city's monstrous deficit.
"This year, it's $525 million that's billed to taxpayers. Next year, it's $625 million. The year after, $675 million. So, at a certain point, the city's going to go bankrupt," he said.
The labor leaders are asking San Francisco Congresswoman and Speaker of the House Nancy Pelosi to support their position.