The Uefa president, Michel Platini, will not be able to dismiss serious questions about his ‘disloyal payment’ from Sepp Blatter with his usual blend of charm, humour and professed naivety

Criminal investigators in Switzerland have taken another walk up to Fifa HQ, that once impregnable bunker high on a Zurich hill, and finally knocked on the door of the president, Sepp Blatter. Five months before the departure he has scheduled after a generational 41 years working at football’s world governing body, Blatter is now the target of criminal proceedings and it will particularly wound him that his own country, where he has always been so cosy, has turned forensic on him.

But Michel Platini – the man who would be king, having declared his candidacy and become the clear favourite to replace Blatter in February’s presidential election – has serious questions to answer about these proceedings, which he has clearly failed to recognise.

The office of the Swiss attorney general, Michael Lauber, which is releasing just enough basic detail about its Fifa investigations to be explosive, announced to the world that one of its two criminal proceedings centred on Blatter concerns a 2m Swiss francs (approximately £1.35m at today’s rates) payment he made to Platini in February 2011. The other involves a television contract signed in 2005 with Jack Warner, the disgraced Caribbean football baron who once threatened Blatter with a “tsunami” of revelations. The Trinidadian did not quite plan, though, for it to happen while he is under indictment by US federal authorities for huge alleged bribery and corruption, which he denies.

Lauber’s office said in its statement that the payment by Blatter was “allegedly” for work Platini had done at Fifa between January 1999 and June 2002 – almost nine years before the money dropped into Platini’s bank account. The football world immediately saw alarm in the timing: spring 2011 was when Platini decided not to run against Blatter for Fifa president and instead endorsed Blatter.

Platini had understood Blatter would step down that year after concluding his third term as president, but, when Blatter went back on that, Platini had the option of running against him. Instead, the Frenchman backed him, and in May 2011 Uefa’s executive committee urged its 53 national associations to vote for Blatter. Now we know that shortly before that Blatter paid him 2m Swiss francs.

The attorney general’s statement made it clear that while Blatter is under suspicion for that “disloyal payment”, a criminal offence, Platini was interviewed on Friday – understood to have been for four hours at Fifa HQ – not as a suspect but as “a person asked to provide information”.

Platini put out a statement stressing that he is not a suspect and he sought to make light of this encounter with criminal investigators, portraying the money – nine years late – as entirely normal. “Regarding the payment that was made to me, I wish to state that this amount relates to work which I carried out under a contract with Fifa and I was pleased to have been able to clarify all matters relating to this with the authorities.”

Greg Dyke, the FA chairman, who backed Platini for Fifa president in July, almost immediately the Uefa president announced his candidacy, offered some characteristically premature and ill-thought out reaction, telling ITV News: “I know no more than you do,” before focusing all his comments on Blatter.

However, Dyke might have been better taking a step back and considering the questions this raises for Platini. They come at a time when Fifa is near collapse with corruption allegations, indictments and arrests and with Platini, president of European football’s governing body, presenting himself as the ideal candidate to clean the whole sorry mess up. These are the highest stakes possible for the integrity of the game and if Platini is to ascend to head Fifa – or even remain as president of Uefa – he has to give grown-up answers to the obvious doubts raised.

For a start, why on earth was Platini being paid in February 2011 for work he did at Fifa, as Blatter’s special advisor, which finished nine years earlier? If it was indeed a payment for that work, does that mean Platini worked for three years at Fifa – before he had another well-remunerated source of salary as Uefa president – without being paid? Why did Fifa not pay him, if that was the case? What did he do for money in that time and what efforts did he make to get Blatter to pay him for the time he had spent advising him – with his contract presumably not being honoured?

Then, why did February 2011 suddenly become the moment chosen for Platini to be paid? How did this happen? Did Platini finally decide it was about time he nagged for the money or did Blatter suddenly discover the yellowing invoices on Platini-headed paper, buried for nearly a decade at the bottom of his in-tray?

Platini also needs to address the question of timing. Why did he endorse Blatter rather than run against him and did it, definitely, have nothing to do with the payment? There is also the question of why Platini is only “a person asked to provide information” while Blatter is a criminal suspect over the same payment. It is difficult to understand why, if the money was owed to Platini on a contract he had with Fifa, however belatedly it was being paid, the settlement of that legitimate debt should be “a disloyal payment”.

Platini, a former great as a player, has in his eight years as Uefa president developed the winning art of dismissing serious questions with a shrug of charm, humour and professed naivety. He has suffered remarkably little pressure over his vote for Qatar to host the 2022 World Cup, which followed lunch at the Élysée Palace with the then French president, Nicolas Sarkozy, and the prime minister and son of the emir of Qatar.

Platini has said he knew Sarkozy supported Qatar and wanted the Qataris to buy and fund Paris Saint-Germain, which they later did, but says his president did not ask him to vote for Qatar and the lunch did not influence him. Platini’s son, Laurent, was then hired as chief executive by the Qatari sportswear firm, Burrda, a recruitment Platini has said was unconnected to his vote and made because Laurent is a capable professional.

For Blatter, the knock on the door must be a nightmare he never dreamed would come to pass in all his years at the top. His would-be successor cannot pretend there are no questions here for him, because that would take world football, and all those who love it, for fools.

Platini needs to respond to this with clarity, or to apply the word being honestly promised for the new reformed Fifa: transparency.