Assaults against subway workers are up 39 percent from last year, the MTA’s largest labor union said Wednesday.

Eight-five workers were assaulted through the first eight months of the year — up from 61 through the end of August 2018, union officials said, citing internal agency data.

The data comes from an internal MTA “Lost Time Accident Report,” the union said, which documented various types of “accidents” that cause transit employees to miss work.

In 2018, the average TWU-repped worker took six workers’ comp days, The Post reported in August.

MTA officials have said worker absences are impacting the agency’s staggering overtime costs, which have spiked 36 percent since 2016 — up to $1 billion last year.

In a statement, Transport Workers Union Local 100 President Tony Utano accused MTA Chairman Pat Foye of intentionally concealing the rising assault numbers.

“How come the MTA isn’t releasing these statistics? These are their numbers,” Utano said. “The silence just reinforces the feeling among transit workers that the MTA and Chairman Foye don’t care about transit workers or their safety.”

The TWU announcement comes as the union negotiates a new contract with the MTA. According to contract documents released by the union, the agency wants to insert language into the contract that would mandate fewer worker absences.

The union’s announcement Wednesday came the day after Gov. Andrew Cuomo bemoaned deteriorating quality of life underground, also citing assaults on workers.

In a statement, MTA spokesman Tim Minton said officials are aware of the problem, and working actively to stem the scourge of worker assaults. Minton pointed to a June initiative from Cuomo and Mayor Bill de Blasio to increase the presence of cops in the transit system.

“Assaults on subway workers are a real concern,” he said. “Transit President Andy Byford personally met this month with Manhattan DA Cy Vance to work towards more aggressive prosecution of, and maximum sentences for, perpetrators.”