U.S. Representative Jesse Jackson Jr., a Democrat from Chicago, on Wednesday submitted a letter of resignation to House Speaker John Boehner, quitting the Congress.

The resignation came in the wake of controversy over Jackson's extended medical leave and an ethics investigation targeting him. In the letter, Jackson said that he has decided to resign to " focus on restoring my health." Jackson has been treated for bipolar disorder.

Jackson also said that he was "aware of the ongoing federal investigation into my activities," and is doing his best to " address the situation responsibly, cooperate with investigators and accept responsibility for my mistakes."

Jackson was dogged by controversy because he took a months-long leave earlier this year to be treated for a "mood disorder" without giving an explanation for what the illness was during that period. He was also being investigated for alleged misuse of campaign funds to decorate his home.

The son of civil rights leader Rev. Jesse Jackson, Jackson won another term during the Nov. 6 election without any campaigning. The seat he vacated would be filled through a special election called by Illinois Governor Pat Quinn.