Aleksander Ceferin says Florentino Perez is "the president of nothing" and believes the controversial European Super League was "an attempt to create a phantom league of the rich".
On Sunday, Real Madrid president Perez was named as chairman of the hugely divisive competition, with Los Blancos named among 12 founding members planning to play in a breakaway league.
However, just two days later, Premier League clubs Manchester United, Arsenal, Chelsea, Liverpool, Manchester City and Tottenham all pulled out amid a huge backlash from the Football Association, the UK government, fans, pundits and players.
Despite the competition crumbling before it got off the ground, Perez launched another staunch defence when speaking to Cadena SER's El Larguero radio show late on Wednesday, having earlier this week stated the Super League was vital for the future of clubs struggling financially in the COVID-19 pandemic.
UEFA chief Ceferin believes Perez and other presidents should not be solely blaming the coronavirus crisis for huge losses, making pointed remarks in an interview with Slovenian broadcaster Pop TV.
"I might want to say something else that Perez said earlier – clubs have losses, but also because they are poorly run," Ceferin said.
"If you overpay players, unsuitable players, and therefore do not achieve a result, it means a loss to you.
"For example, Bayern Munich have no losses and have won the Champions League. You cannot just blame COVID-19, which many do.
"Perez is the president of a Super League that didn't exist. At the moment he's the president of nothing.
"Perez would like a [UEFA] president that will listen to him and a president that will do as he tells him. But I am trying to work in European and world soccer's best interests.
"I'm actually horrified that by being enormously rich, profit means so much more than values. You can tell lies; you can enter players and the coaches into a new competition without them knowing anything about it."
Perez insists the idea of the Super League is not dead in the water, but Ceferin remains convinced it was little more than a power play to try to protect the interests of football's richest clubs.
"In my opinion, the Super League never existed," Ceferin added.
"It was an attempt to create a phantom league of the rich that wouldn't follow any system, that wouldn't take into account the pyramid structure of football in Europe, its culture, tradition or history."
Perez bizarrely cited a lack of interest from the younger generation among reasons for wanting to form the league, even suggesting matches could be shortened from the current time of 90 minutes.
But Ceferin again disputed the point, adding: "Young people are very interested in a football match, it's completely clear to me.
"The fact is that football is a sport, it's a passion, a school of life, you can learn a lot from football. I learned a lot from football myself.
"You can't look at football as a product, you can't look at the players as customers or consumers, you can't look at how many you have in your account or how many new followers you have on Twitter instead of the result after the game. This has become common with certain big club owners and they have simply lost touch with reality and reality was clearly shown in the UK 24 hours or so ago."