Joan Laporta has hit out at Paris Saint-Germain's ability to throw money at players, claiming the Ligue 1 champions are 'kidnapping players for money'.
Barcelona were never in the race for Mbappe, who surprised Real Madrid when he chose to extend his stay in Paris, but they have felt the financial might of PSG in the past when they lost Neymar for a cool €222m back in 2017.
In an interview with L'Esportiu, the Barcelona president did not hold back in voicing his displeasure towards PSG's business.
"This distorts the market," he said of Mbappe's extension. "Players end up being kidnapped for money.
"These are the effects of a club having a state behind it. This goes against all the principles of the European Union. It is a reflection on the sustainability of football in Europe.
"From a Barcelona perspective, there is a direct rival that does not come out stronger and we are glad that he cannot make us squirm when it comes to competing, but I'm left reflecting on the sustainability of football, because I don't think we should care so much about a rival either.
"We have to worry about having a competitive team, which is what we are trying to do. It has been seen that when we have cared more about ourselves than our rivals, things have gone well."
Talk then turned to Neymar, who Laporta described as a 'slave' to the PSG system.
"Who doesn't love Neymar? He is an exceptional player," Laporta began.
"He has a contract with PSG, he has four or five years left. These players who have signed for clubs like PSG, have almost signed their slavery. For money."
Laporta was not as critical of Lionel Messi's departure to the Ligue 1 side last summer and admitted he would be open to re-signing both the Argentine and Neymar, but only if they were made available on free transfers.
"Messi's exit is what it is," he said. "We would all have liked him to end his sporting life here and for whatever reason he has not been able to. It could be because of the 'fair play' of the Spanish league and the proposal of PSG.
"These players, when they enter a dynamic like PSG, find that they cannot leave because the operations are many millions of euros. In the case of Neymar, I don't know how they do it in France, because they have other systems that we don't have here, but cancelling a contract that is signed in advance costs a lot of money. Obviously, PSG have a state behind them, they have a lot of money and maybe could afford to terminate such a contract.
"All these players, if they want to come back to Barça, should come free one day. We are not in a position to make a purchase which can cost these sorts of transfer fees. But even if we had the budget, we wouldn't do it. It would be irrational.
"If they are players who are free and on the market, then they are of exceptional quality and we have already enjoyed them at Barça. Then it would be a matter for the coach to think about whether or not they can fit into the new Barça project.
"As players, I like both of them very much."