Violent attacks by inmates against each other and on Department of Correction officers at Rikers Island spiked over the past year even as the jail population dropped, according to new city statistics.

The overall “rate of violent incidents among individuals in custody rose by 24.5%, and the rate of serious injury to individuals in custody as a result of these incidents rose by nearly 24%,” according to the mayor’s annual Management Report released Tuesday.

Slashing and stabbings jumped by 10.4%. Assaults against staff also rose 3.4% percent, leading to a staggering 37% increase in serious injuries to Department of Correction officers, the report found.

“There’s really little to no consequence to the inmate for fighting or for bad behavior,” Joseph Russo, president of the Deputy Wardens Association, told The Post.

“So the inmate is not concerned about that when he has a fight with another inmate or assaults staff,” Russo said.

The report, authored DOC Commissioner Cynthia Braun, attributes the rise in violence to the declining inmate population that’s part of de Blasio’s plan to close Rikers by 2027.

“As the Department’s overall population has declined, DOC is managing a population made up of individuals with more serious offenses,” she says in the report.

“From Fiscal 2018 to Fiscal 2019, the percentage of the population with confirmed gang affiliation rose from 15.4 percent to 16.4 percent.”

Th city’s average daily jail population dipped below 8,000 for the first time last year since 1980.

A DOC spokesman said: “Safety is our top priority, and as the jail population continues to fall, we are now managing population of people charged with more serious offenses.”

The spokesman added, “We recently expanded body cameras to all officers at the George R. Vierno Center on Rikers Island, and we will continue to implement initiatives like these to increase safety.”