A Republican ex-congressman trying to win his seat back in New Hampshire is denying allegations that he may have "used his office" to build his stock portfolio, a charge that comes after his once-robust poll numbers took a downward turn. 

Republican Charlie Bass at one point seemed a shoo-in for the open District 2 seat, a chance for the GOP to expand its foothold in liberal New England. But his pre-primary lead has all but vanished since Democrat Ann McLane Kuster won her primary, and an article Thursday detailing questionable financial dealings didn't help matters.

The Nashua Telegraph reported that during his last year in Congress in 2006, Bass' financial disclosure forms showed he bought at least a half-million dollars in stock in a local wood pellet company run by his nephew. The report suggested he helped the firm while in office by setting up a meeting with a Bush administration official and writing a tax rebate bill that could benefit the company. 

Bass said the information on his disclosure form was a typo. He explained that even though his 2007 form showed he bought the shares in January and November of the prior year, he actually bought them in January 2007 after he lost his race to Democrat Paul Hodes, who is now running for Senate. He told the newspaper he first inquired about them in November 2006. 

Bass spokesman Scott Tranchemontagne confirmed to FoxNews.com that the forms reflected a "clerical error" which will be corrected in an amended report. He said the ex-congressman did not use his office to help the company. 

But his opponent's campaign said Bass still has some explaining to do. The article served as fodder for Kuster during a debate Thursday morning. 

"Even by Congressman Bass's own account, he used his office to promote his nephew's company and then got rewarded with over $500,000 worth of his company's stock just days after leaving office, in a private deal not available to the public," Kuster Campaign Manager Colin Van Ostern said in a statement to FoxNews.com. "That is what is wrong with Washington, and Bass's denials leave a lot of questions unanswered." 

The Telegraph story said the New England Wood Pellet firm credited the ex-congressman with setting up a meeting in early 2006 between company President Steven Walker, who is married to his niece, and then-Energy Secretary Samuel Bodman. Bass also wrote a bill to give a tax rebate for firms that, among other things, buy wood pellet stoves. The rebate didn't end up in the 2006 Bush administration budget, but New England Wood Pellet reportedly promoted it. 

He later joined the company's board of managers after leaving office. His stock had at least doubled by the end of 2008, the Telegraph reported. 

Tranchemontagne, though, said the tax bill benefited alternative energy investment across the country. And he said Bass in no way arranged the Bodman meeting, despite the company's claims. He explained that Bodman spoke with Walker in the course of a scheduled stop by the secretary at a well-known energy company. Several other industry representatives were there. 

"It was more of a press event than a meeting," Tranchemontagne said. "For Ann Kuster or her Democratic attack machine allies to suggest that this was in any way some kind of secret meeting or improper get-together is complete and utter fabrication." 

He added: "Did Charlie make a clerical error on his disclosure form? Yes. That's it." 

The latest poll on the race by The Hill newspaper showed Bass leading by 3 points, within the 4.9 percent margin of error. Bass at one point was leading by as much as 18 points, before the primary. 

But Tranchemontagne said the pre- and post-primary polls are not comparable. 

"Her name ID back then ... was exponentially lower than it is now," he said. "Of course her number's going to go up."