A former top in-house lawyer for the Port Authority of New York and New Jersey admitted he created a bogus retainer agreement from Weil, Gotshal & Manges promising discount legal services.

Christopher Hartwyk, 53, of Newark, pleaded guilty in Manhattan Criminal Court on Friday to a second-degree misdemeanor count of offering a false instrument for filing, a Class A misdemeanor punishable by up to a year in jail.

In March 2009, Hartwyk, then deputy general counsel, had been instructed to obtain discounts from outside counsel when he provided the retainer letter to the Port Authority’s Law Department, according to Manhattan District Attorney Cyrus Vance Jr. The document stated that Weil Gotshal would bill at a 15 percent discount, though the firm had made no such offer. Hartwyk also forged the signature of a Weil Gotshal partner, Vance said.

Port Authority Inspector General Robert Van Etten said, “The effect of Mr. Hartwyk’s conduct was to deny the Port Authority the opportunity to save money on its legal expenses.

Hartwyk’s lawyer, Marc Agnifilo of Brafman & Associates, did not return a call Monday. Weil Gotshal spokesman Robert Lennon did not provide a comment by press time.

Hartwyk was appointed to the agency in 2003 by New Jersey Gov. James McGreevey, initially as deputy solicitor in the Law Department. In January 2012, Hartwyk was replaced by outgoing N.J. Attorney General Paula Dow, who was appointed by deputy general counsel by Gov. Chris Christie.

In March 2012, Hartwyk joined Newark’s Genova Burns Giantomasi Webster, where he handled complex commercial litigation as well as infrastructure, transportation and logistics. He made partner that August but left the firm in June 2013. According to managing partner Brian Kronick, “Published reports indicate that the activities at issue in Mr. Hartwyk’s circumstance predated his employment with this law firm.”