Tebas made his remarks during an appearance at the Soccerex football conference in Manchester on Wednesday.
He said City and French giants Paris Saint-Germain were “destroying football” with state-enabled spending.
But a City spokeswoman, in a statement released late on Wednesday, said: “Mr Tebas’s statements are ill-informed and in parts pure fiction.
“As you would expect, Manchester City Football Club and the City Football Group are seeking appropriate legal counsel and will act accordingly on that advice.”
PSG prised Neymar from Barcelona in a world-record 222 million euros ($265 million) deal and have also signed Kylian Mbappe from Monaco in a move that could be worth 180 million euros.
City outspent any other European club in the transfer window by lavishing around £221 million (242 million euros, $288 million) on new players.
Tebas said the assistance City and PSG received from their respective Emirati and Qatari backers amounted to “financial doping”.
He said the two clubs were “laughing” at European governing body UEFA’s Financial Fair Play rules, which oblige clubs to minimise their losses.
UEFA has opened an investigation into PSG’s transfer dealings, but City are not under investigation.
In particular, Tebas raised questions about the legitimacy of City’s decision to loan five players to Girona for the coming season, suggesting the players had been undervalued.
Asked if City and Girona were “trying to cook the books”, Tebas replied: “They were trying to, but they didn’t manage to do it.”
City purchased a 44.3 percent stake in Girona last month, matching the stake already held by City manager Pep Guardiola’s brother Pere.
Girona were promoted to the Spanish top flight last season.
Tebas is reported to have held a meeting to discuss the matter with City chief executive Ferran Soriano on Wednesday.
France’s Professional Football League has strongly criticised Tebas.
“These unworthy remarks are unbecoming of an institution as respectable and successful as the Spanish Liga,” the LFP said.
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