Republican presidential candidate Ben Carson has announced the resignation of his campaign finance chairman Dean Parker, who has come under scrutiny for lavish spending.

The Alabama-based entrepreneur helped Carson raise tens of millions of dollars. But Parker also presided over an operation known for its exuberant spending. Politico recently reported that Parker himself earned $20,000 per month.

Carson has recently slipped in national polls amid infighting among his inner circle and questions about his qualifications. Carson lost his campaign manager and communications director in December.

The retired neurosurgeon did not acknowledge any of those struggles in a statement, praising Parker as "a valued" aide and "trusted friend."

Parker's departure comes on the morning of one of the last two GOP debates before voting begins with the Feb. 1 Iowa caucuses.