Federation Internationale de Football Association have called for an investigation into City's financial dealings, but the club have strongly denied the accusations.
Mancini signed two contracts on the same day - one a base £1.45 million a year for City, before bonuses, and the other a base £1.75 million with the Abu Dhabi, paid into an offshore shell company in Mauritius called Sparkleglow Holdings.
The magazine claims that in an internal email, City's chief financial officer Jorge Chumillas wrote: "We will have a shortfall of 9.9m pounds in order to comply with UEFA FFP this season".
City have subsequently been accused in more leaked documents of an array of attempts to inflate and backdate sponsorship deals to "deceive" UEFA.
Federation Internationale de Football Association said the claims were an attempt to "undermine" Infantino.
Der Spiegel also reported last Friday that Man City threatened to destroy UEFA with legal action before reaching a 2014 settlement to forfeit 20 million euros ($22.8 million) in prize money.
And while the club have given only a short response to the allegations to date, on Tuesday boss Pep Guardiola insisted City's success is not exclusively down to the money they have spent.
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He said "late early" ballots, which don't get counted on Election Day, now are undergoing a signature-verification process. Angela Green, a Green Party candidate, was running a distant third, with just over 2 percent of the vote.
Af for the FFP complaints, he stuck to the club's version: "I am part of the club and I support them completely". Of course we want to follow the rules, from UEFA and Federation Internationale de Football Association and the Premier League. UEFA, FIFA and the Premier League, they do what they have to do.
"Believe me, I'm completely honest, I don't know what happened, because I am a manager, I am focused about what happened on the pitch, and locker room".
In addition, Jose Mourinho has stated that he suspected Manchester City of these kinds of wrongdoings from several years. "I have thoughts from a few years ago but I keep the thoughts to myself, "he said at his pre-match press conference ahead of United's clash with Juventus on Wednesday. We want to do what we have to do in terms of the rules".
Since Man City was bought with Abu Dhabi sovereign wealth in 2008, a team long in the shadows of more glamorous Manchester United has overtaken its rival on the field.
Italian manager Roberto Mancini was sacked in 2013, just after City had failed to defend their first Premier League title and lost the FA Cup final. UEFA's rules are created to encourage clubs to live within their means and prevent fatcat owners, many of them with unlimited funds, from buying their way to success to the detriment of less affluent rivals.
In its latest claims, Der Spiegel says City used "creative solutions" including selling players' image rights to an external company, therefore writing off that cost from their accounts. "UEFA FFP compliance WILL NOT be achieved".