Former head of the Boston Federal Bureau of Investigation Kenneth Kaiser pled guilty in federal court on Thursday that he had illegal contacts with the bureau after he was retired when he had meetings with agents as a private consultant.

Kaiser, 57, resident of Hopkinton, was released on personal recognizance and faces no prison time for now. For a violation of ethics, the maximum sentence Kaiser could face is up to one year in prison and a fine of $100,000. Instead, the prosecutor, Diane Freniere, is striking a plea agreement with him and recommending that he pay a $15,000 fine and serve no prison time. U.S. District Court Judge F. Dennis Saylor IV is not bound by the pact, and could enforce the maximum fine should he find that sentence more appropriate.

Kaiser declined to comment after the hearing at the U.S. District in South Boston.

An ethics law by the U.S. Department of Defense prohibits professional contact from senior executive branch personnel with their former agency for one year after they leave the office.

Anthony Fuller, Kaiser’s defense attorney, said in a Thursday statement that Kaiser’s communications to FBI employees were not meant to be secretive.

“All of his communications to his former colleagues in the FBI were made in the good faith that he was helping their law enforcement mission,” he said. “He did not contact his former colleagues through secret means or back channels, but did so openly and obviously and, in one instance, attended a meeting inside the U.S. Attorney’s office in Boston.”

In July 2009, Kaiser retired from the FBI and Freniere said he was hired as a consultant by LocatePlus, an online investigative database, to handle an internal investigation into the company’s chief executives Jon Latorella and James Fields.

“Kaiser knowingly made — with intent to influence — communications with his old office through phone calls, emails and in-person meetings regarding the FBI’s own probe into LocatePlus,” she said.

In March 2010, Kaiser became a full-time employee of the company, acquiring the title of director of government sales. The company provides public information on bankruptcies, real estate transactions and drivers’ licenses to commercial, private sector and law enforcement entities.

Despite the gag order, Freniere said Kaiser earned $8,000 selling LocatePlus products to the FBI.

Latorella pleaded guilty in 2012 for security fraud and Fields was convicted by a jury. Both are serving five-year prison sentences.

Kaiser also admitted to improper contacts with the FBI while he was working for a Gloucester company in 2009, who asked him to investigate a threatening letter they received. They paid him $5,700.

“He wanted the FBI to take charge of the investigation and he was supplying the FBI with information on a particular suspect,” she said.

Kaiser served as assistant director of the FBI’s Criminal Investigation Division for two years in Washington, D.C., dealing with all of the agency’s U.S. criminal investigations before he retired. Previously, he served as the special agent in charge of the FBI’s Boston office from April 2003 to December 2006. He worked for the FBI for about 27 years.

Kaiser is scheduled to be sentenced on Dec. 17.