Updated and corrected

Rep. Markwayne Mullin (R-Okla.) may have violated House ethics rules and federal laws by earning outside income beyond permissible levels last year, according to a new congressional watchdog report released Monday.

But the House Ethics Committee stopped short of establishing a special committee to further investigate the allegations against Mullin. It is unknown whether the secretive panel might take further action.

Mullin, 36, is a freshman lawmaker whose family owns five plumbing companies in Oklahoma employing more than 120 people. He continues to personally advertise for the companies and serves as an officer or board member for the companies in violation of House rules and standards of conduct, according to a report released by the committee.

The report by the Office of Congressional Ethics details how Mullin earned more than $600,000 from the plumbing companies last year. He characterized some of the income as "distributions" from one of the companies that is now directly owned by his wife. But the income far exceeds the $26,955 limit placed on outside income for House lawmakers and also violates rules prohibiting lawmakers from sitting on a company board, the report said.

Mullin also has continued serving as the "face and voice" of his family's plumbing companies by advertising for them on a weekly home improvement-themed radio show and on radio, television and Internet video commercials, the report said. The radio show, "House Talk with Markwayne Mullin," is advertised as a way "to save big bucks by doing home improvement projects yourself or by finding the right contractor for the job." During the program, Mullin and other home contractors answer listener calls on home improvement. The show has aired on a Tulsa news/talk radio station for several years.

Jan Baran, an attorney for Mullin, said in response to the OCE report that the lawmaker was working to undo his business practices on the advice of the Ethics Committee that he sought after winning his House seat in 2012. Mullin and his family "spent thousands of dollars and substantial business hours" to restructure the businesses in a way consistent with House ethics rules, Baran said. The OCE also "grossly exaggerates" the amount of money Mullin earned from the companies and emphasized that the income was distributions and not earned income.

In his response, Baran suggested that questions about Mullins's businesses should be handled by the Ethics Committee as an advisory matter and that it shouldn't have been investigated by OCE as a possible act of wrongdoing.

As part of its decision, the Ethics Committee reserves the right to establish a separate panel to further investigate the charges. The move announced Monday, known as "Committee Rule 18(a)," is similar to what happened to then-Rep. Rob Andrews (D-N.J.). When Andrews faced allegations of improperly using campaign funds to pay for personal travel, the ethics panel kept the investigation open and later established a separate panel to further investigate the charges. Andrews resigned last month as the investigation was reportedly nearing its conclusion.

Correction: A previous version of this article incorrectly identified Jan Baran as a woman.