FIFA president Gianni Infantino is coming under mounting pressure to explain his role in the failed European Super League project, sources have told ESPN.

Publicly under the banner of FIFA, Infantino has renounced last month's breakaway which saw 12 clubs including Manchester United, Real Madrid and Juventus launch a new competition to shatter the existing structure of European football, only to collapse within 48 hours in the face of fierce opposition from fans, league administrators and politicians.

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However, La Liga chief Javier Tebas has named Infantino as "W01," a key figure outlined in the Super League documentation drawn up by legal firm Clifford Chance which has since been seen by ESPN.

Condition One in the working draft which all competing clubs had to sign up to states: "The implementation of the SL Project is subject to the obtaining of a final and binding official decision taken by W01 in accordance with the terms included in Scheduled 8.2 (the W01 Condition)."

W01 is thought to stand for "World Number One" and a senior source at a top European club has confirmed to ESPN that this is Infantino.

Sources at two other clubs involved in the project have also told ESPN that they were led to believe during negotiations to join the Super League that FIFA were on board.

The key point, they argue, is that the clubs driving the proposal would not have launched the breakaway without having some sort of assurance that this condition would be met.

Sources told ESPN a project of this magnitude -- with damaging repercussions for failure -- would have received encouragement from the highest echelons of football administration before making the decision to launch. There is therefore widespread dismay among a host of big European clubs at an alleged disparity between Infantino's public position and the one many believe he may have taken in private.

"With this kind of thing you have to see the origin of those rumours, I speak with European teams and it was known that such a project was being prepared," Infantino said last week. "When I was at UEFA, there was already a similar project, but it was corrected.

"At FIFA we have the obligation to speak to everyone, but we aren't behind the Super League, in January I signed a statement making clear what we thought, the break with certain clubs was very clear for a long time, but we're not going to kill the dreams of other clubs, a closed league is something FIFA stands against."

FIFA and football's six regional confederations released a statement in January claiming a "closed" European league would not be recognised. It has been suggested this was interpreted by those plotting a breakaway that a tweak to the plans was required: the project was eventually designed to have 15 permanent members and five qualifying teams entering each year.

Sources have also pointed out FIFA were the last major governing body to publicly condemn the Super League after its launch. Infantino spoke out against the plans on April 20 and that night, English clubs Chelsea and Manchester City began the exodus of clubs withdrawing.

ESPN has also learned of some of the tactics involved in convincing clubs to sign up to the Super League, particularly in the days leading up to the launch on Sunday April 18.

One top European club, "Club A" were wavering over whether to commit and were told by a third party that a rival, "Club B," had joined the breakaway league, applying further pressure on them to sign up. A Club A executive phoned a counterpart at Club B and was told categorically it wasn't true.

"Who do you believe in that situation?" a source said. "Do you join the train leaving the station or stand your ground and take a club at their word? Someone was obviously lying. The amount of lying going on at the highest level among clubs was unbelievable. Relationships have been irreparably damaged in some cases."

Barcelona, Juve and Madrid are the only teams yet to sign a "Club Commitment Declaration" with UEFA. While the other nine have done so and been reintegrated into the existing structure, that trio face huge fines and potential bans from the Champions League and Europa League for refusing to give up on the Super League project.

Infantino was UEFA general secretary from 2009-2016.

FIFA, asked for comment by ESPN, has not yet replied.