The Chicago Board of Ethics has fined David Plouffe $90,000 for illegally lobbying the mayor on Uber's behalf, according to the Chicago Tribune.
Uber was facing hurdles operating at Chicago airports, due to pick-up fees and requirements to display placards, the Tribune reported, so Plouffe contacted Chicago Mayor Rahm Emanuel.
But the board of ethics voted that Plouffe broke the rules when he failed to register as a lobbyist, according to the Tribune.
Both Plouffe and Emanuel have ties to President Barack Obama. Plouffe, who now works with Facebook's Mark Zuckerberg, joined Uber after serving as Obama's campaign manager. Emanuel served as Obama's chief of staff.
Though Plouffe doesn't dispute the allegations, the fine is far above the $1,000 minimum, the Tribune said. Uber will be fined $2,000, the Tribune reported.
"We work hard to ensure our registrations are accurate and up to date," an Uber spokesman told CNBC. "We regret that in this instance we made a mistake and we will comply with the board's assessment."