City were believed to be ahead of the queue to acquire Messi when the Argentine demanded a transfer from Barcelona in August. However, Messi withdrew his request to terminate his contract 10 days later to avoid a legal wrangle with the Catalonian outfit.
Messi's Barcelona deal expires next June, allowing him to walk away from the Camp Nou for free if he doesn't extend his paperwork.
"The only club in the Premier League that talks about registering Messi is Manchester City," Tebas said in a news conference Tuesday when asked about the prospect of Messi leaving Spain, according to ESPN's Sam Marsden.
"Since Man City compete outside the rules, what I am worried about is that they are able to access a player by breaching UEFA's rules. It is not only me complaining about this. (Liverpool manager Jurgen) Klopp and (Tottenham Hotspur's Jose) Mourinho have also complained about City."
Tebas added La Liga is "ready" should Messi decide to leave and claimed it hasn't "noticed any difference" from the departures of Neymar to Paris Saint-Germain in 2017 and Cristiano Ronaldo to Juventus in 2018, as quoted by BBC Sport's Simon Stone.
UEFA declared Manchester City guilty of breaking its financial rules and banned the club from European competitions for two years. City maintained their innocence, and the Court of Arbitration for Sport cleared them of breaking UEFA's guidelines in July.
"I have criticized what City do so many times, doing it one more time makes no difference," Tebas said. "They are not affected by COVID-19, by pandemics, or by anything because they are financed differently and it's impossible to fight against that."
Sheikh Mansour, a member of Abu Dhabi's royal family, took over City in 2008. The ownership group has since spent large amounts of money on the club's facilities and in the transfer market to turn it into one of the strongest forces in the European game.