The release came following pressure from various sources, including GOP rival Mitt Romney, who has also called on the former U.S. House speaker to release documents detailing a House ethics investigation against him.
The Freddie Mac contract was released by The Center for Health Transformation, an operation of the Gingrich Group LLC. NBC News reported the release did not include any written or produced reports resulting from Gingrich's work for Freddie Mac under the 2006 contract released Monday.
NBC said Gingrich's 1999 contract with Freddie Mac, and its 2002 renewal, were not released.
The 2006 contract did not specify the work Gingrich performed but indicated he reported to Freddie Mac's top lobbyist, Craig Thomas. The contract called for Gingrich to be paid $25,000 per month, with a cap of $300,000, The Washington Post reported.
Romney, speaking in Tampa, Fla., said the ethics investigation into Gingrich when he was House speaker could show "potentially wrongful activity of some kind," the Post reported.
"We could see an October surprise a day from Newt Gingrich," Romney said. "And so let's see the records from the ethics investigation, let's see what they show. Let's see who his clients were at the time he was lobbying Republican congressmen for Medicare Part D. Was he working or were his entities working with any healthcare companies that could've benefited from that? That could represent not just evidence of lobbying but potentially wrongful activity of some kind."
Neither Romney nor his advisers offered evidence that they knew of "wrongful activity" by Gingrich. Romney has been trying to blunt Gingrich's recent surge in the polls and his win Saturday in the South Carolina primary.
In 1997 a House ethics panel's investigated allegations Gingrich improperly used a college course, funded by political donors, to promote political causes, potentially violating federal tax laws and House ethics rules. The House voted 395 to 28 to adopt the committee's report that recommended reprimanding Gingrich and imposing a $300,000 penalty.
Florida's presidential primary is Jan. 31.
Romney, who has taken heat from fellow GOP candidates and Democrats for not releasing his tax returns during his time as chief executive officer for investment firm Bain Capital, urged Gingrich to return the money he was paid by Freddie Mac.
"He said in a debate, actually, that people who profited from the failed model of Freddie Mac and Fannie Mae ought to give back their money," Romney said. "Well, the speaker made $1.7 million in his enterprises from providing services to Freddie Mac. He ought to give it back."
Gingrich has said repeatedly he never lobbied on behalf of Freddie Mac and healthcare entities, describing his work as being a consultant and historian.