European Super League president Florentino Perez warned Manchester United and Manchester City before the duo backed out on Tuesday night.
Both United and City controversially agreed to become founding members of the new Super League that would guarantee qualification for 15 clubs each season, though only 12 were initially confirmed on Sunday evening.
It was reported each of the founding teams would receive around £350million for signing up with Perez claiming the competition is critical to save football from financial peril.
Fans, pundits and almost the entirety of European football quickly rallied against the plans and all six English clubs involved - United, City, Chelsea, Liverpool, Arsenal and Tottenham Hotspur - pulled out last night.
Threats of legal action from the Premier League and UEFA emerged on Tuesday morning and the six parties eventually caved to mounting pressure.
However, they could now be in a spot of bother with the Super League after Real Madrid chief Perez warned clubs against pulling out of the deal in an interview with El Chringuito.
"The contract of the Super League is binding. Nobody can leave, we will work all together," he said on Monday night. "All the clubs signed the contracts last Saturday - there's no problem."
Speaking about why the Super League was formed, Perez explained: "Many important clubs in Spain, Italy and the UK want to find a solution to a very bad financial situation.
"The only way is to play more competitive games. If instead of playing the Champions League, the Super League helps the clubs to recover the lost earnings.
"Here at Real Madrid we have lost a lot of money, we are all going through a very bad situation.
"When there is no profit, the only way is to play more competitive games during the week.
"The Super League will save the clubs financially."
