A handful of Members of Congress have among them received hundreds of complaints from the Federal Election Commission about inaccuracies in their campaign finance reports over the past several years, far beyond the average of most campaigns.

The FEC routinely sends letters to campaigns asking them to explain records that appear to be incorrect; since 2003, the agency wrote more than 18,000 letters to 3,300 candidates, according to a Roll Call study of campaign finance records.

But several Members of Congress have received more than their share of queries.

No one has received more of these questions than Rep. Henry Cuellar. As the Texas Democrat raised and spent more than $5 million, he also racked up 63 notifications from the FEC since 2003 questioning his campaign finance reports.

These agency notifications often included strong language and warned the campaign that it could face "an audit or enforcement action" if it did not adequately answer the FEC's concerns.

The agency ultimately did audit Cuellar's 2006 campaign, finding that he received $36,000 that exceeded contribution limits and $13,000 in prohibited corporate contributions as well as misstated financial activity on numerous records.

Cuellar's campaign spokesman explained that many of the filing errors were a symptom of the lawmaker's transition from the Texas Legislature to the more stringent federal filing requirements of the U.S. House.

"When going from raising $200,000 a year to raising millions of dollars, there are inevitably going to be some growing pains," said Colin Strother, Cuellar's campaign spokesman. "And I - quite frankly - underestimated how much more difficult it would be."

Originally the campaign used staff familiar with state requirements to file FEC reports, Strother said. But during the last few years, the Cuellar campaign retained new accounting staff inside the Beltway, and Strother does not anticipate any future problems.

"We are in full compliance," he said. "We are not currently under any sanction or any investigation by the FEC, and we have always fully complied with any directive they have given us."

Other campaigns have had more serious problems at the staff level. For instance, many of the FEC's 39 letters to Sen. Lindsey Graham (R-S.C.) during the past seven years stem from a scheme by the campaign's former administrator, Jennifer Adams, to embezzle nearly $280,000. An internal review by the campaign exposed numerous unauthorized disbursements, and in 2008 Adams pleaded guilty in state court to several counts of fraud.

Graham's former campaign manager, Scott Farmer, said an overwhelming number of the FEC letters resulted from the situation of embezzlement and its paperwork aftermath.

While some lawmakers can point to actions of campaign staff, others who received a significant number of letters said software problems were to blame for the misunderstandings between campaigns and the FEC.

"The majority of requests for additional information occurred during years when my campaign was using FEC-approved software which had a hidden flaw causing recurrent errors," Rep. Peter King (R-N.Y.) said in an e-mail. He has received 42 letters since 2003.

"Once this software problem was identified, we changed software and since then have had minimal requests for additional information (such as father and son having same name), each of which has been readily complied with."

While some lawmakers discussed extenuating circumstances, Rep. Roscoe Bartlett did not defer any blame for his campaign finance issues.

"I take full responsibility for my campaigns," said the Maryland Republican, whose 49 FEC letters since 2003 rank as the second-most among federal lawmakers. "I'm certainly not perfect, but I'm honest and I've got the audit to prove it."

Following notifications questioning Bartlett about disbursements, disparities in cash on hand, and even the failure to file a pre-primary report, the FEC audited his 2008 campaign. The recently released audit found 21 unreported transactions but no intentional wrongdoing.

Some Congressional staffers explained away the frequency of the FEC's questions.

Democratic Congressional Campaign Committee Chairman Steve Israel's staff said all of the agency's 44 letters on issues ranging from disclosure of debts to reimbursements have been answered by amendments filed by the campaign.

"These sorts of commission requests are very common, and the FEC has been satisfied with the campaign's responses," said Lindsay Hamilton, the New York Representative's communications director. "The campaign received only three letters during the 2010 cycle on minor questions and responded to each of them."

It is not just individual campaigns that receive questions from the FEC. Including political action committees, joint fundraising committees and other campaign entities, the commission has sent out 48,000 requests for clarification in the past seven years.

"That is an alarming number," said Craig Holman, a lobbyist for Public Citizen who monitors campaign finance laws. "When there are that many letters, it also strongly suggests that there are a lot of problems going on."

Leading the way was the Republican Party of Minnesota with 153 letters since 2003.

"We went through a couple different accounting people and they frankly made mistakes in our reports," state party Chairman Tony Sutton said. "It was kind of a headache to go through all of that but we fixed those mistakes and hopefully it is all behind us."