According to Press TV, 54-year-old Brinkley, a former Vice Chairman of the Oklahoma Senate's Finance Committee, admitted Friday he had stolen $1.8 million from a nonprofit agency where he worked for 16 years.
In 2015, the Better Business Bureau accused Brinkley of setting up fake corporations in order to pay his bills and support a gambling habit.
Brinkley worked as president and CEO of the Better Business Bureau in Tulsa from 1999 to 2011 and continued his job there as chief operating officer until last year, when the BBB sued him for defrauding the agency.
According to investigators, Brinkley created fraudulent invoices for services not rendered and then submitted them to the BBB claiming they were legitimate expenses.
During his tenure at the BBB, he also paid his personal expenses using the agency's money.
On Friday, the former Republican state senator pleaded guilty in US District Court to five counts of mail fraud in addition to one count of subscribing to a false tax return.