Burris was appointed by disgraced former Illinois Gov. Rod Blagojevich, who was impeached and driven from office after he was accused of trying to sell the Senate seat.
The committee cited at least one example, a phone conversation with the governor's brother, where Burris linked his willingness to raise funds for the governor with appointment to the Senate.
While finding no violation of law, the committee's "Public Letter of Qualified Admonition" told Burris that "Senators must meet a much higher standard of conduct" than he exhibited with his constantly changing statements.
The ethics committee has often been criticized for failing to go beyond letters of admonition after finding a senator's conduct discredited the institution.
Burris commented, "I am pleased that after numerous investigations, this matter has finally come to a close. I thank the members of the Senate Ethics Committee for their fair and thorough review of this matter, and now look forward to continuing the important work ahead on behalf of the people of Illinois."
Weakened and facing multiple primary challengers next spring, Burris has decided not to fight for a full Senate term next year. Fellow Democrats shun him. Meanwhile, the former governor is scheduled to go to trial in June.
The ethics committee was especially critical of Burris' comments during the Nov. 13, 2008, phone call from the governor's brother.
While Robert Blagojevich explicitly told Burris he was calling to raise campaign funds for the governor, the committee's letter to Burris said "you appeared to agree to write a check and even potentially raise money"; and "repeatedly brought up your desire to seek the Senate seat.
"You also implied that the people you might raise money from would be unhappy if you did not receive the appointment," the committee wrote. The committee found the conversation "inappropriate in its content and implications."
The letter also was critical of Burris' shifting explanations about his contacts with the governor or his representatives. The committee found:
-In his Jan. 5, 2009 affidavit to the Illinois House of Representatives, Burris said he did not have contact with Gov. Blagojevich or any of his representatives about an appointment to the Senate before Dec. 26, 2008. Burris was appointed to the Senate by Blagojevich four days later.
-In his Jan. 8, 2009 testimony before the committee to impeach the governor, Burris - despite repeated questions on the subject - did not disclose having any conversations about his desire to seek the appointment, or about fundraising, with anyone associated with the governor except former Blagojevich top aide Lon Monk.
-It was not until Burris' second affidavit and subsequent press statements that the senator disclosed additional contacts with associates of the governor.
"You gave multiple and at times contradictory explanations for failing to disclose all your contacts with the governor's associates, which individually and collectively gave the appearance that you were being less than candid," the ethics panel wrote.
The committee said that in deciding to go no further than the letter, it considered that a county prosecutor found Burris' sworn statements did not violate the law.
"We were also aware that these issues surrounding your appointment to and seating in the Senate have been subject to intense public criticism," the committee said.
The second-ranking Senate Democrat, Dick Durbin of Illinois, said, "When we met with Roland Burris in January, we made it clear that in order for him to be seated in the U.S. Senate he needed to appear before the Illinois General Assembly to testify openly, honestly and completely about the nature of his relationship with the former governor, his associates and the circumstances surrounding this appointment.
"Since then, the accuracy and completeness of his testimony and affidavits have been called into question. The U.S. Senate Ethics Committee has completed its review into this matter and found that Sen. Burris actions have brought discredit on him and the Senate. The letter of qualified admonition from the Ethics Committee speaks for itself."