( CNN ) -- A spokesman for Illinois Sen. Roland Burris resigned Thursday in the wake of new disclosures about requests that Burris raise money for disgraced former Gov . Rod Blagojevich while seeking a U.S. Senate appointment . Sen. Roland Burris , who is under fire to resign , arrives at a Chicago City Club luncheon to speak Wednesday . `` I initially began helping the senator on a temporary basis because he is a long-term friend who I served several years when he was [ Illinois ] attorney general , '' Jason Erkes said in a written statement to CNN . `` It is now time for me to get back to focusing on ... my newly formed strategic communications business . '' The statement did not comment on the new disclosures . A defiant Sen. Burris insisted Wednesday that he was innocent of any wrongdoing in his appointment to President Barack Obama 's former Senate seat , as calls for his resignation intensified . The Senate Ethics Committee has launched an investigation in the wake of disclosures that Burris spoke with Rod Blagojevich 's brother about possibly raising money for the former governor . The Sangamon County , Illinois , state 's attorney is also considering whether to file perjury charges against Burris . Watch the latest on the chorus for Burris to resign » . `` I 've done nothing wrong , and I have absolutely nothing to hide , '' Burris said in a speech to the City Club of Chicago . `` You know the real Roland ... Stop the rush to judgment . '' Burris told reporters earlier in the week that he informed Blagojevich 's brother Robert in November that it would be inappropriate to raise money because he was interested in a Senate seat . During his testimony under oath in Blagojevich 's impeachment trial , however , Burris failed to mention any such conversations when asked about contacts with the governor 's office . He later acknowledged that his testimony might be incomplete and filed an affidavit correcting it . Burris said Wednesday that he did not hide his desire to be appointed to the Senate , but never had a conversation about a possible appointment with anyone close to Blagojevich other than the former governor 's attorney . He also insisted that nobody from Blagojevich 's office contacted him to discuss a potential appointment . iReport.com : Should Burris resign ? `` The governor 's brother reached out to [ me ] to do fundraising , '' Burris conceded . `` But I did not give one single dollar to the governor . '' Illinois ' senior senator , Dick Durbin , a member of the Senate Democratic leadership , told reporters during a congressional trip to Europe that `` the Ethics Committee of the Senate is undertaking an investigation . '' `` Everyday there are more and more revelations about contacts with Blagojevich advisers , efforts at fundraising and omissions from his list of lobbying clients , '' Durbin later said in a written release . `` This was not the full disclosure under oath that we asked for . `` These news reports and the public statements by Roland Burris himself are troubling and raise serious questions which need to be looked at very carefully . '' CNN 's Peter Hamby , Brianna Keilar , Dierdre Walsh contributed to this report .
Mike Erkes , a spokesman for State Sen. Bob Burris , steps down . New questions arising over Burris ' appointment to Senate . Allegations Burris not honest about ability to raise cash for campaign . Erkes does n't mention probe , says he will focus on his new campaign .