Manchester City showed a "blatant disregard" to Uefa's investigation into potential Financial Fair Play (FFP) breaches, says the Court of Arbitration for Sport (Cas), even though it found "no conclusive evidence that they disguised funding from their owner as sponsorship".
Last month, Cas overturned City's two-year ban from European competition and the club's fine was also cut from 30m euros (£26.9m) to 10m euros.
While City were criticised for a "severe breach" by failing to co-operate with Uefa the club did provide Cas with all of the emails that had formed the basis of Uefa's charges.
Cas' written findings said the panel found "no adverse inferences" could be drawn from City's failure to produce evidence.
The club said it co-operated "in the face of a shifting and still unparticularised case involving allegations of fraud and conspiracy" and the reason Uefa knew about the disputed transactions is because the club co-operated and "explained those transactions in great detail".
The club added it was not required to comply with every demand made of them by Uefa, just those "proper" and "reasonable" requests that were "relevant" to decision-making.
Earlier this month, Cas overturned the two-year ban, saying that most of the alleged breaches of FFP rules were either not established or time-barred.
The club were, however, punished for failing to co-operate with Uefa's process after failing to provide substantial amounts of evidence until they took the case before Cas.
Uefa began its investigation into City after German newspaper Der Spiegel published leaked documents in November 2018 alleging City had inflated the value of a sponsorship deal, misleading European football's governing body.
Reports alleged City - who have always denied wrongdoing - deliberately misled Uefa so they could meet FFP rules requiring clubs to break even.
"The panel is of the view that Uefa by no means filed frivolous charges against City but, based on the evidence, the panel cannot reach the conclusion that disguised funding was paid to City," the report, released on Tuesday, said.
It added: "City's failure to co-operate with the investigation is a severe breach and City are to be seriously reproached."
The documents also reveal that in March 2020 nine Premier League clubs filed an application for intervention to Cas "opposing any possible application by City" to be allowed to play in Europe next season pending an appeal decision. This was before the Cas hearing.
However, as City never made such an application, it was never processed. The nine Premier League clubs who made the application were Arsenal, Burnley, Chelsea, Leicester, Liverpool, Man United, Newcastle, Tottenham and Wolves.
In its report, Cas said Uefa maintained the club "on countless occasions refused to answer questions, refused to provide documents, refused to arrange for the attendance of requested persons and - ultimately - it even instructed its own expert witness not to answer specific questions".
However, Cas said it only found two specific requests in which City failed to comply with its duty of co-operation.
Uefa said the case represented "the most serious, sophisticated, deliberate and fundamental attempt to circumvent and violate basic financial fair play principles". It said the "attitude of the club" should also be considered, given it gave "demonstrably incorrect information and continues to change its explanations".
It added the "evidence on record is overwhelming" and consists of the Football Leaks Documents and accounting evidence.
However, Cas said the burden of proof lay with the governing body and the majority of its panel found Uefa did not satisfy such burden.
Dan Roan, BBC sports editor
This document appears to weaken the suggestion - made by some observers since the verdict was announced two weeks ago - that Manchester City won their appeal on "a technicality".
City fans can draw little comfort from the fact that charges relating to communications company Etisalat were disregarded because they were more than five years old. And Cas makes clear that Uefa's charges were made "on a legitimate basis". It also suggests that City could have won the initial case with Uefa, avoiding a huge amount of time and expense, had they just co-operated earlier.
But Cas concludes that "no adverse inferences can be drawn from City's failure to produce evidence" and crucially, finds "no evidence that agreements were backdated, or that City tried to cover up any alleged violations" with regards to their Etihad sponsorship.
Uefa's case was found to have relied on "insufficient evidence", and City are understood to feel fully exonerated, and justified in not co-operating with Uefa's investigation on the basis they believed the initial hearing was biased.
But the panel do not see it that way, and pull no punches with their criticism of City's obstruction, referring to "a severe breach... blatant disregard" which warrants "serious reproach".
Those words, and one of the biggest fines in football history, is undoubtedly damaging to the club's reputation after years of success on the pitch.
But ultimately, the fact City remain in the Champions League after this saga, and have been acquitted of the main charge of self-sponsorship, means they have still secured a qualified but crucial victory.