Fifa's investment plan has intensified tensions between Fifa president Gianni Infantino and Uefa.

"On information and belief, Infantino's actions described herein rise to the level of criminal mismanagement." "A stunning dereliction of duty." "A fraudulently off-market price promoted by Infantino for his own benefit." Just some of the blistering language used by Uefa's lawyers in legal papers lodged in the United States over Fifa president Gianni Infantino's now-shelved plan to sell off stakes in competitions to private investors.

A scheme, Uefa claims, that awarded the World Cup an "absurdly low enterprise value... that was neither the product of an open, competitive auction, nor tested by any independent valuer". All part of "a transaction that inflicted direct and concrete injury... to the detriment of Fifa as well as its 211 members", and was conducted under "a veil of secrecy".

The court documents, which reference Infantino's "cronies" and "co-conspirators", and include a chapter on "the enduring history of corruption among Fifa officials", request access to evidence and documents in the US for use in potential litigation in Switzerland against Infantino.

More than a month since the Fifa Forward Enterprise plan (FFE) was revealed, before collapsing days later, this increasingly acrimonious civil war shows little sign of ending. Since then, we have seen the strongest public pressure from those opposed to Infantino with a series of cutting statements, including from former players, politicians, and fan groups.

And there was even the leaking of claims - labelled "categorically untrue" by Infantino - that his alleged lover was given a severance payment over the affair while he was at Uefa. Now we have the threat of legal proceedings.

It is ironic that Infantino has enjoyed arguably his best week since this saga began. On Thursday, he received the qualified backing of the powerful Saudi Arabian Football Federation, which said that "at this time [it] supports the continued efforts of Gianni Infantino to restore unity".

Despite defying calls from three confederations and various other stakeholders to stand down, Uefa's decision to drop its threat of boycotting Fifa competitions after receiving assurances there would be no repeat of the FFE scheme was seen as another victory for him.

But Uefa then raised the stakes. News that it was preparing criminal legal proceedings was viewed as a dramatic escalation, and evidence that it was not backing down in its determination to oust Infantino.

Although Infantino defended FFE as a means of unlocking the commercial potential of Fifa, before later apologising for "errors", neither he nor Fifa have responded to this latest twist, with officials insisting they are focused on delivering the U20 Women's World Cup, starting next week in Poland.

Gianni Infantino, meanwhile, fresh from trips to the Dominican Republic and Paris last weekend, posted video of a "wonderful" visit to Vietnam, the latest stop on what is increasingly resembling a world tour aimed at shoring up support.

Given that Uefa first warned of potential legal action almost a month ago, when it instructed Fifa to retain any "relevant materials" related to the plan, Infantino may well have anticipated Uefa's move, so how might he feel now?

Josh Kushner (right) is the founder of venture capital firm Thrive Capital, earmarked as the lead investor in FFE. Much may depend on whether US courts side with Uefa over its requests for disclosure of evidence related to the FFE plan.

In documents seen by BBC Sport, it is seeking information from three parties; Fifa, Thrive Capital - the venture capital firm earmarked as the lead investor in FFE along with its founder Josh Kushner, and former Formula 1 chief Greg Maffei, who is described as "the key commercial adviser" on the proposed deal.

While the filings state that neither Kushner or Maffei are anticipated defendants in any proceedings, in the case of Kushner for instance, Uefa's lawyers say they are seeking subpoenas for "the production of documents and communications and for deposition testimony".

Although Kushner, who is the brother of US president Donald Trump's son-in-law, is yet to comment, some legal experts believe he could successfully challenge and block such a subpoena request by arguing that the details of the deal need to remain confidential to protect his business interests and future investments. Kushner has recently agreed a deal to buy basketball's Los Angeles Lakers for a record £9.3bn.

It is unclear how long this process could take, or whether Uefa will secure the evidence it needs to support its claim that the World Cup was deliberately undervalued at about £15bn. Nor is it clear whether it will ultimately follow through on its threat to lodge a criminal complaint in Switzerland.

How confident Uefa would be of criminal charges being brought is also highly uncertain. In 2002, in echoes of the current disunity, several Fifa executive committee members filed a criminal complaint against former president Sepp Blatter with a Zurich court, external. The public prosecutor took no action, while Blatter denied wrongdoing.

Last year, a long-running attempt by the Swiss Attorney General's Office to prosecute Blatter and former Uefa president Michel Platini ended with both men being fully cleared of corruption charges.

"What Uefa have to show is that they have an arguable case for criminal proceedings to be brought against Infantino," says leading sports lawyer Nick de Marco KC. "If they can show that…then they ought to be given disclosure of a lot of the documents."

When asked what he thought the chances were of the case eventually going to trial, De Marco said: "We're a long way off from that - the first stage is this disclosure application. My own view is that the likelihood of success in that, which is very important, is high, but then it's a question for the Swiss prosecutor, looking at that disclosure, to decide whether there is a case [and] that will take some time...but I think what we will likely see is disclosure of very interesting documents and more light shone onto this plan."

Perhaps aware of the challenges its legal action could face, Uefa has in the meantime pledged to "secure fundamental reform, restore proper limits on presidential authority and ensure that Fifa is once again governed as an institution - not around one individual", while demanding "a genuinely independent external review of FFE".

Given the support he retains in South America, Africa and parts of Asia, and how he has survived everything Uefa has thrown at him in recent weeks, many still expect Infantino to remain in power and seek re-election for a fourth term in the spring.

Uefa has warned that, should he do so, it will "join forces with its partner confederations to ensure that member associations are offered a credible alternative - one committed to integrity, accountability, development and genuine institutional change".

But how likely is it that a unifying challenger will emerge? And how can the game avoid a repeat of such a crisis in future?

This video can not be played. Uefa 'will continue to fight' Infantino - Uefa vice-president Laura McAllister.

"We have some clarity over the changes that are needed to modernise football governance and to make it run in a way that is accountable to its most important stakeholders," Uefa vice-president Laura McAllister told BBC Sport in Monaco.

"I think there are lots of credible candidates out there, but it has to be a candidate that can unite that standpoint and somebody who has the credentials and the credibility and the buy-in to really champion that agenda.

"We need to make the governance itself rooted on the principles that are so important like transparency and independence and critical challenge and due diligence. We knew this wouldn't be a simple process and we knew that change wouldn't happen overnight.

In October, Infantino will finally come face-to-face with some of his opponents at what could be a highly charged first Fifa Council meeting since the rebellion over FFE. The following month, presidential candidates must be nominated. Then, in March, an election is scheduled that, if contested by Infantino, could prove pivotal to the future direction of football.

Until then, the division and rancour that has engulfed the world's game in this remarkable drama of intrigue and power looks set to continue. And right now, reunification seems hard to imagine.

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