The practice is outlawed in the UK but in Spain and Portugal the practice is very common. Bruno de Carvalho, elected Sporting president in March 2013, argued that the funds are a “menace” and a “monster” that undermine clubs’ finances, football’s integrity and poses a risk of increasing match-fixing.

Sporting are refusing to fulfil the contract the club signed with Doyen Sports, the offshore fund, which claims it is entitled to seventy-five percent of the €20m Manchester United paid last month for Marcos Rojo.

They have repaid the €4m which Doyen originally loaned the club for the three-quarters share in Rojo’s economic rights but the club are refusing to pay a further €11m.

Doyen are expected to sue for the money but Bruno de Carvalho believes that the contracts the club signed under the previous management were in breach of FIFA regulations, which prohibit third parties from buying “the ability to influence” team selections or transfers.

De Carvalho said the contract the club originally made with Doyen was invalid and claimed that Sporting did not want to sell Rojo, who played for Argentina in the World Cup final, but Doyen offered the player for sale over the club’s head, ‘to Manchester United and all the world.’

The Sporting president went on to state that when he was elected he arrived to find the club’s finances were “a disaster”, they were €500m in debt, and the majority of the players were owned by funds, some having bought 95%, 90% or 80% of the players’ rights. “I am against funds where we don’t know where the money is coming from, and who try to manipulate football,” de Carvalho said.

“Many times there are similar owners who are connected with the funds and gambling companies, so match-fixing is the worst fear now for football. Everybody sees the problem.”

UEFA has pledged to ban third-party ownership, with the president, Michel Platini, opposed to the practice of players being “owned” by offshore investment funds. FIFA has a working party examining the issue.

Doyen Sports responded by arguing that it provides clubs with “much-needed” money, linked to the future value of players, which enables them to hold on to players and compete, citing Atlético Madrid as “a perfect example”.

Regarding the dispute with Sporting over the Rojo’s transfer, a Doyen spokesman insisted the contract was valid: “We categorically do not manage or influence the player and we ensure that it is written into every contract we have with the club. This is the first ever issue we have had and it is with a specific president who now wants to renege on a bona fide contract that his club has signed. We welcome taking the matter to court.”