Manchester City have dismissed as "entirely false" accusations that they may have flouted Financial Fair Play rules after UEFA launched a formal investigation into the claims.
The European governing body announced on Thursday evening that it had opened a probe into allegations made by a series of media outlets, principally German magazine Der Spiegel, suggesting that the club has circumvented FFP rules.
However, City provided a swift and robust response, welcoming the investigation and insisting they had done nothing wrong.
A statement on the club's official website, www.mancity.com, said: "Manchester City welcomes the opening of a formal UEFA investigation as an opportunity to bring to an end the speculation resulting from the illegal hacking and out of context publication of City emails.
"The accusation of financial irregularities are entirely false. The club's published accounts are full and complete and a matter of legal and regulatory record."
City's response was delivered a matter of minutes after UEFA confirmed that it is to look into claims, which involve aspects of the Premier League champions' financial affairs such as sponsorship and transfers.
UEFA said in a statement: "The Investigatory Chamber of the independent UEFA Club Financial Control Body has today opened a formal investigation into Manchester City FC for potential breaches of Financial Fair Play (FFP) regulations.
"The investigation will focus on several alleged violations of FFP that were recently made public in various media outlets.
"UEFA will make no further comments on the matter while the investigation is ongoing."
The development is the latest in a saga which has unfolded over several months, with Der Spiegel having based its stories on information from a series of leaked emails.
The magazine has alleged that City have deceived UEFA over their sponsorship deal with Etihad, claiming that only £8million of the £67.5million deal they struck in 2015 came from the airline, with the remainder being provided by club owner Sheikh Mansour via his Abu Dhabi United Group.
In addition, the magazine has claimed City paid a then 14-year-old Jadon Sancho's agent £200,000 in relation to the deal that took the now Borussia Dortmund midfielder to the Etihad Stadium from Watford, a payment which would have been in breach of Premier League rules governing the signing of players aged under 16.
The latest Der Spiegel allegation centred around Argentinian midfielder Bruno Zuculini's arrival at the club in 2014, while Danish newspaper Politiken has also suggested that City have recruited African players for free through FC Nordsjaelland's Right to Dream programme under an agreement between the two clubs.
City have always dismissed the claims as a smear campaign and have responded on each occasion with the same official statement.
It said: "We will not be providing any comment on out of context materials purported to have been hacked or stolen from City Football Group and Manchester City personnel and associated people.
"The attempt to damage the club's reputation is organized and clear."
UEFA's investigation may or may not vindicate the club, although the penalty if any wrongdoing is identified could be far-reaching.
The governing body's chief FFP investigator Yves Leterme revealed in an interview with Belgian magazine Sport and Strategy earlier this year that the ultimate sanction may go as far as expulsion from the Champions League.
Leterme said: "If what has been written about Manchester City is true, there might be a serious problem. This can lead to the heaviest punishment – exclusion from UEFA competitions."
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