According to the FEC, Bartlett's committee understated the amount of money it received by more than $37,000 out of $360,000. Included was a failure to report eight donations from political action committees totaling $7,300.

FEC auditers compared bank records with Bartlett's public disclosure reports and found that his campaign failed to report 63 separate payments, totaling $67,000 (out of overall spending of $272,000). The unreported spending appeared to have been mainly for political advertising and operating expenses, the FEC said.

The FEC did not say specifically why it had conducted the Bartlett audit but did say it generally launches investigations when a campaign committee appears to have not met basic requirements for compliance with federal election law.

In response to the audit, Bartlett's campaign amended its financial reports in a series of filings over the last four months. Bartlett had $416,000 in his campaign account as of the end of June, according to his most recent FEC filing.

"I strive to be as frugal with donations from supporters to my campaign as I am with taxpayers' money," Bartlett said in a statement relayed by his office. "I have been very lucky to benefit from superb volunteers for my campaign rather than paying pricey professional consultants. I was gratified and I hope Sixth District residents and supporters of me will be pleased that the routine audit by the FEC found that there was no missing money or misuse of funds by my campaign. Mistakes identified in reporting have been corrected. The bottom line is that this FEC report reassures the public that above all, I'm honest, not perfect, but honest. When I make mistakes, I acknowledge and correct them."

Bartlett is a heavy favorite to win re-election and faces only token opposition in next month's Republican primary. Two Democrats, Casey Clark and Andrew Duck, are competing for their party's nomination against Bartlett.