Mayor de Blasio’s troubled Administration for Children’s Services employed a convicted killer as a juvenile counselor — without running a mandatory criminal background check — and he assaulted a child in his care, officials said Tuesday.

ACS Commissioner David Hansell, who blamed the bad hire on his predecessor, admitted he didn’t know how many more of his 7,000 employees have felony records. He ordered “spot checks” in a desperate scramble to try and find out.

Jacques Edwards, 55, served three decades in prison for murder, attempted murder and other charges in Brooklyn before being hired by the ACS in March 2014, less than two years after he was sprung on parole, records show.

On Friday, a surveillance camera caught Edwards — who is 6-foot-3 and weighs 225 pounds — assaulting a 6-year-old boy inside an ACS youth shelter in Manhattan, authorities allege.

A criminal complaint says Edwards picked up the kid and pushed him against a door to “in effect” open it, then put him in the top drawer of a filing cabinet before “shoving him head-first into the cabinet.”

The boy suffered a scrape to his left temple and was treated by a nurse at the Nicholas Scoppetta Children’s Center in Kips Bay, court papers say.

Edwards was charged with two counts of assault, one a felony, and endangering the welfare of a child. He was arraigned in Manhattan Criminal Court on Monday night and sent to the Tombs on $15,000 bail.

A spokeswoman for the state Justice Center for the Protection of People with Special Needs said its records show that Edwards “was never submitted for a background check by ACS, as required by law.”

Agencies that provide services to children, the mentally ill and people with disabilities have been required to have the Justice Center screen job applicants and volunteers since June 30, 2013, according to Justice Center spokeswoman Christine Buttigieg.

Edwards’ base salary during fiscal 2017 was $38,616, but he only earned $25,772 after going on leave in fiscal 2016, according to city payroll data.

Hansell said Edwards wouldn’t have been hired under policies revised when he replaced ex-Commissioner Gladys Carrion, who resigned in disgrace in late 2016 following the beating deaths of two children known to ACS.

“Our own current protocols for positions like this are very different and much stricter than they were when he was hired,” Hansell said.

Hansell added ACS now followed Justice Center rules that bar hiring anyone with a felony conviction for a sex crime, a violent crime within the past 10 years, or crimes involving child abandonment or endangering the welfare of an elderly, incompetent or disabled person.

ACS applies an even “higher standard” to anyone working with children, he said.

The agency has started conducting running “spot checks on individuals who were hired previously . . . to make sure they meet our current standards,” he added.

Asked afterward whether ACS had the Justice Center run a criminal background check on Edwards, a spokesperson said the Department of Citywide Administrative Services handled its criminal background checks and ran the check on Edwards.

DCAS didn’t respond to requests for comment last night.

But Buttigieg said, “Section 378-a of the Social Services Law requires ACS to run a background check through the Justice Center, so our statement stands.”

With Rebecca Rosenberg