Retired United Auto Workers official Michael Grimes, right, exits the U.S. courthouse in Ann Arbor, Michigan, after pleading guilty to federal corruption charges on Wednesday, Sept. 4, 2019. His attorney Michael P. Manley is being interviewed in blue suit.

ANN ARBOR, Mich. – As leaders with the United Auto Workers union negotiate a new contract this week with General Motors executives, a former union negotiator admitted in court to receiving at least $1.5 million in kickbacks from union vendors.

Michael Grimes, a retired senior official with the union's GM division, pleaded guilty Wednesday to charges of wire fraud and money laundering. He faces up to 20 years in prison for the charges, however prosecutors recommended Grimes serve 46 to 57 months. Sentencing is scheduled for Jan. 14 in Detroit.

Prosecutors have not publicly connected GM or its executives to Grimes as they did with a separate corruption case involving Fiat Chrysler and UAW executives. There also have not been allegations Grimes' actions were meant to impact the UAW's negotiations with GM as there was with the Italian-American automaker.

"The conduct admitted by Mr. Grimes in his plea today is shocking and absolutely disgraceful," the UAW said in a statement, adding that it has since implemented a slate of changes meant to clean up its internal contracting process. GM reiterated the company is "deeply disturbed" by the conduct of Grimes and other union officials that has been uncovered by the government's ongoing investigation.

"These actions represent a stunning abuse of power and trust," GM said in an emailed statement. "There is no excuse for union officials to enrich themselves at the expense of the union membership they represented."

Grimes' guilty plea was part of a deal with federal prosecutors. Michael P. Manley, Grimes' attorney, declined to comment as to whether or not his client is cooperating with prosecutors for the ongoing investigation.

"Mr. Grimes is devastated by his actions," Manley, standing in-front of Grimes, told reporters after the hearing. "He has over 30 years devoting his time to the UAW. He loves the UAW. He's crushed by what he has done to their reputation and is owned up to his actions and is going to suffer great consequence because of that."

Grimes, while answering questions from prosecutors and U.S. District Judge Bernard Friedman, said he was facing "financial burden" as a reason for his crimes. Grimes, standing in a black suit with a silver checked tie, offered little other insight into his actions aside from answering direct questions. Grimes' salary was $140,000 in 2017, his last year of full employment with the UAW before retiring last year.