Manchester City have been banned from European club competitions for the next two seasons and fined £25m (NZ$50m), after being found to have committed "serious breaches" of financial regulations.
The back-to-back defending English Premier League champions overstated sponsorship revenue in accounts submitted between 2012 and 2016, according to European football's governing body Union of European Football Associations (UEFA).
City said in response they are "disappointed but not surprised" by UEFA's announcement and will appeal against the punishment to Court of Arbitration for Sport (CAS).
"The Adjudicatory Chamber, having considered all the evidence, has found that Manchester City Football Club committed serious breaches of the UEFA Club Licensing and Financial Fair Play Regulations by overstating its sponsorship revenue in its accounts and in the break-even information submitted to UEFA between 2012 and 2016," read a UEFA statement.
City said they are "disappointed but not surprised" by UEFA's announcement and will appeal against the punishment to CAS.
"Manchester City is disappointed but not surprised by today's announcement by the UEFA Adjudicatory Chamber," read a club statement.
"The club has always anticipated the ultimate need to seek out an independent body and process to impartially consider the comprehensive body of irrefutable evidence in support of its position.
"Simply put, this is a case initiated by UEFA, prosecuted by UEFA and judged by UEFA.
"With this prejudicial process now over, the club will pursue an impartial judgement as quickly as possible and will therefore, in the first instance, commence proceedings with the Court of Arbitration for Sport at the earliest opportunity."
In the absence of a successful appeal, Pep Guardiola's side would be unable to compete in the competition until the 2022/23 campaign.
Findings published by UEFA also state that the club "failed to cooperate in the investigation of this case by the CFCB".
If City's appeal is unsuccessful and they finish in the top four of the Premier League this season, the team which finishes in fifth position will replace them in next season's Champions League.
Financial Fair Play (FFP) was introduced by UEFA as an attempt to prevent clubs getting into serious financial difficulty by overspending.
Regulations, which must be adhered to by all clubs participating in UEFA competitions, were drawn up in 2009 and introduced at the start of the 2011-12 season, with clubs required to balance their books over the course of three years.
After previously being punished in 2014, City accepted a settlement that included a fine, a limit on transfer spending for the current season, and a 21-man limit on Champions League squad size, instead of the usual 25.
UEFA opened a fresh investigation into City following a series of new allegations about the club in the media, led by German magazine Der Spiegel.
It was alleged that City's breaches of FFP around the same period ran much deeper than UEFA realised at the time of the 2014 settlement.
On Friday, Guardiola claimed he could get sacked if Manchester City fails to win the Champions League.
"I want to win the Champions League, I dream and will enjoy the games against Real Madrid, to see what I can do,"he told Sky Sports UK.
"And this process, the two weeks before, will be the happiest moments of my profession, to imagine what we can do to beat them.
"If we don't beat them, then the chairman will come, or the sporting director, and say 'It's not good enough, we want the Champions League, I'm going to sack you.'
"Then 'OK, thank you, it was a pleasure.'"