Manchester City have vowed to appeal after being banned from European competition for the next two seasons for "serious breaches" of financial regulations.
The Premier League champions claim a UEFA investigation into accounts submitted by the club between 2012 and 2016 was "flawed" and "prejudicial".
City, who have also been hit with a fine of 30million euros (£24.9million), said they were "disappointed but not surprised" by the governing body's verdict and will swiftly refer the case to the Court of Arbitration for Sport.
The heavy sanctions relate to an alleged overstatement of sponsorship revenue in the club's efforts to comply with Financial Fair Play (FFP) regulations.
"Manchester City is disappointed but not surprised by (Friday's) announcement by the UEFA Adjudicatory Chamber," read a Manchester City statement.
"In December 2018, the UEFA chief investigator publicly previewed the outcome and sanction he intended to be delivered to Manchester City, before any investigation had even begun.
"The subsequent flawed and consistently leaked UEFA process he oversaw has meant that there was little doubt in the result that he would deliver
"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."
FFP was introduced by UEFA at the start of the 2011/12 season as an attempt to prevent clubs falling into serious financial difficulty by overspending.
All clubs competing in UEFA competitions are expected to operate within their means and meet break-even targets, while dealings have to be transparent.
Should City's appeal fail and, as expected, they finish in the top four of the Premier League, their Champions League place for next season would pass on to the club which finishes fifth, as outlined under clause 4.08 of UEFA's Champions League regulations.
Newly-promoted Sheffield United currently occupy that spot, with Tottenham, Wolves, Everton, and Manchester United just behind and each in contention to potentially benefit from City's predicament.
The PA news agency understands City manager Pep Guardiola has been kept fully informed of the situation by his club and it will be business as usual for the time being.
Spaniard Guardiola has won two Premier League titles, an FA Cup, and twice lifted the League Cup since arriving at the Etihad Stadium in 2016, but European glory has proved elusive.
His current contract runs until the summer of 2021.
Findings published by UEFA also state that City failed to cooperate in the investigation of the case, which was conducted by independent Adjudicatory Chamber of the Club Financial Control Body (CFCB).
UEFA's statement read: "The Adjudicatory Chamber, having considered all the evidence, has found that Manchester City 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.
"The Adjudicatory Chamber has also found that in breach of the regulations the Club failed to cooperate in the investigation of this case by the CFCB.
"The Adjudicatory Chamber has imposed disciplinary measures on Manchester City Football Club directing that it shall be excluded from participation in UEFA club competitions in the next two seasons (ie. the 2020/21 and 2021/22 seasons) and pay a fine of 30 million euros."
City will be able to fulfil their last-16 two-legged Champions League tie with Real Madrid, which begins later this month, before their two-season expulsion begins next term.
UEFA opened a fresh investigation into City, who had been previously punished with a fine in 2014, 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.
PA understands the club are unsure how long the appeal process will take but are prepared to be patient as they fight a perceived injustice.
