BOSTON (AP/CBS) – U.S. Rep. Joe Kennedy III says his campaign improperly spent $1.5 million earmarked for the general election during the Massachusetts congressman’s failed bid to capture the Democratic nomination for a U.S. Senate seat.

Kennedy said in a statement on Friday that he did not know about the improper spending before the Sept. 1 primary election and has since reimbursed the campaign with $1.5 million of his own money.

“After an internal review, I believe it was an honest mistake by those involved, resulting from misinformation, not malintent,” Kennedy said in the statement. “But as the candidate, I take full responsibility for the error that occurred and have worked to rectify it as expeditiously as possible.”

Rep. Joe Kennedy III. (Photo by JOSEPH PREZIOSO/AFP via Getty Images)

He and his campaign self-reported the violation to the Federal Election Commission last week.

Federal campaign finance rules do not allow candidates to spend money earmarked for the general election.

Incumbent U.S. Sen. Ed Markey defeated Kennedy in the primary.

(© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)