The findings that led to Uefa’s club financial control body (CFCB) deciding that Manchester City were guilty of a “serious breach” of financial fair play regulations and imposing a two year Champions League ban have finally been revealed in the judgment of the court of arbitration for sport, which overturned the CFCB’s decisions.

The CFCB found after its investigations and hearings that the Abu Dhabi United Group (ADUG), the company through which Sheikh Mansour of the Abu Dhabi ruling family owns City, had funded payments in 2012 and 2013, understood to be £15m each year, that were reported to the Football Association and to Uefa as independent sponsorships from the telecoms company Etisalat.

Related: Verdict that kept Manchester City in Europe delivers some glancing blows

The Cas panel of three European lawyers decided by a majority 2-1, however, that it would not consider the legitimacy of those Etisalat payments, because they were made more than five years before the CFCB charges were brought in May 2019, so were “time-barred”.

Uefa’s rules for the CFCB, whose members are appointed to oversee compliance with FFP, state that “prosecution is barred after five years” for all breaches of FFP regulations.

The senior European lawyers in the CFCB’s adjudicatory chamber (AC), and experienced academics, former politicians and executives in the investigative chamber (IC), considered May 2014 as the date of City’s breach. That was when City agreed an FFP settlement with Uefa, based on the club’s reporting of its finances, which included that Etisalat, a Middle East telecoms giant headquartered in Abu Dhabi, had paid the sponsorship itself.

In fact, the judgment recites, the AC found that ADUG had funded the payments, and that: “The management of [MCFC] was well aware that the payments … made by [a third party on behalf of ADUG] were made as equity funding, not as payments for the sponsor on account of genuine sponsorship liabilities.” The judgment notes that although City and Etisalat had agreed a sponsorship deal in principle in 2012, the actual contract was concluded only in January 2015, and was stated to be retrospectively effective, from 1 February 2012.

In public statements throughout the process, City had accused the members of the IC, AC and Uefa itself of bias against the club, claiming they ignored “irrefutable evidence”. The Cas judgment makes no suggestion of bias, and states that “Uefa by no means filed frivolous charges against MCFC. As also acknowledged by MCFC, there was a legitimate basis to prosecute MCFC.”

The Cas judgment also contains the extraordinary revelation that the panel’s chairman, Rui Botica Santos, a Portuguese lawyer, was recommended by City. Cas rules for appeals state that each party chooses one arbitrator, then the chairman is selected by the chairman of Cas’s own appeals arbitration division. No explanation has yet been given for why City suggested the chairman for this case, although the judgment notes that Uefa did not object.

Some European sports lawyers, speaking to the Guardian, have questioned the independence of the panel member nominated by City, Andrew McDougall QC, a partner in the international law firm White and Case. McDougall was chair of his firm’s operations council for Europe, the Middle East and Africa, from 2016-2018, which includes an office in Abu Dhabi. That office lists Etisalat as a client, and the Abu Dhabi airline Etihad, whose sponsorships were also central to the case, as well as several Abu Dhabi state enterprises.

Related: David Silva adulation shines light on curious denial of Touré’s greatness | Jonathan Liew

The Cas rules state that “arbitrators must be independent, [having] no particular connection with any of the parties”. There is no suggestion of actual bias on the part of either of City’s nominated arbitrators.

City’s position is understood to be that McDougall himself has not acted for those Abu Dhabi companies although his firm has, and that the club’s hierarchy recommended him because of his strong reputation as a lawyer. Uefa did not respond to a question about whether it raised any objection to McDougall’s appointment. McDougall declined to respond to questions from the Guardian about whether he had an apparent conflict of interest in sitting on the case.

Uefa’s nominee was Ulrich Haas, a German law professor based in Zurich, a long-term arbitrator on Cas panels.

The Etisalat evidence, as well as the more widely reported allegations relating to City’s Etihad sponsorship, was a principal reason underpinning the AC’s findings that City were guilty of a breach serious enough to warrant a two-year ban and €30m fine. The FFP rules, introduced by Uefa in 2010-11 to encourage responsible financial management by clubs, limits the cash owners can pour in, which makes independent sponsorships more important for boosting revenues. Like all relationships between clubs and sports governing bodies, the system relies on trust and honest reporting.

The allegations relating to Etihad’s sponsorship were based on City’s own internal emails, published as “leaks” by the German magazine Der Spiegel in November 2018, prompting the IC to ask City for an explanation. The emails included three from City’s then chief financial officer, Jorge Chumillas, to Simon Pearce, a senior City executive, setting out that in 2012-13, 2013-14 and 2015-16, direct funding from Etihad was only £8m, with ADUG funding the rest, which was £59.5m in 2015-16. One email to Pearce enclosed invoices for the sponsorships, with only £8m charged to Etihad.

Citywere found to have obstructed and failed to cooperate with the CFCB’s investigations, but they gave the Cas panel more cooperation, with executives including Pearce providing evidence and appearing as witnesses, insisting that Etihad funded the whole sponsorship. Sheikh Mansour himself also provided a letter, stating: “I have not authorised ADUG to make any payments to Etihad, Etisalat or any of their affiliates in relation to their sponsorship of MCFC.” On the basis of the further evidence it considered, the Cas panel found the Etihad charge to be “not established”.

The judgment reveals that on 9 March this year, nine other Premier League clubs wrote to Cas opposing any attempt by City to seek a “stay of execution” allowing them to play in Europe next season if the appeal hearing was delayed. The clubs were Arsenal, Burnley, Chelsea, Leicester, Liverpool, Manchester United, Newcastle, Tottenham and Wolves. But three weeks later City told Cas it had not requested a stay of execution. Cas agreed with City that the clubs’ claim was therefore “moot”.