(CNN) - U.S. Rep. Cathy McMorris Rodgers, a rising political star who gave the Republican response to the State of the Union address last week, is under investigation by the House Ethics Committee for allegations she improperly mixed campaign money and official office funds to finance a bid for a party leadership post.
McMorris Rodgers won the House Republican Conference chairmanship - the fourth-highest position in the GOP leadership - after the 2012 election, beating Rep. Tom Price of Georgia.
As one of only 19 women out of more than 230 House Republicans, McMorris Rodgers frequently serves as the top spokeswoman for the Republican Party's outreach to women.
The Ethics Committee revealed its investigation on Thursday in a statement. It acknowledging that the matter had been referred to the panel in December by the independent Office of Congressional Ethics.
A source close to the inquiry told CNN that a former staffer for McMorris Rodgers filed the initial complaint.
According to House Rules, members are allowed to use money from personal campaign accounts and official office allowances to cover costs incurred in leadership races. But there are restrictions on mixing the two and on the types of activities that can be paid for with the funds.
Nate Hodson, a spokesman for McMorris Rodgers, responded to the investigation.
"We are confident that every activity was compliant with all federal laws, House rules, and standards of conduct. We are fully cooperating and look forward to seeing this matter dismissed," he said.
In a statement to CNN, McMorris Rodgers' attorney called the investigation "an unfortunate rite of passage for many members of Congress" and said she has "fully cooperated" with the OCE.
"We are confident that the committee will ultimately find that the allegations were baseless and that her office always followed all laws, rules and standards of conduct," Eliot Berke said.
The Ethics Committee said it would announce its "course of action" by March 24.