Third-party ownership of any player is prohibited at English clubs – but in Portugal having a share of footballers' economic rights is still common practice

A quarter of the £21m Chelsea paid to Benfica for the Brazil defender David Luiz was banked not by the Lisbon club but by the investors in a fund to which Benfica sold 25% of David Luiz's "economic rights" for €4.5m (£3.8m) 18 months ago. Luiz was one of 12 Benfica players whose rights were partly sold immediately after the Benfica Stars Fund, run by Banco Espirito Santo, Portugal's biggest bank, raised €40m and began in business in September 2009.

When Chelsea paid £21m for the Brazil centre-back in the frenzy of transfer deadline day, the fund became entitled to a quarter, £5.25m (€6.11m), a profit of €1.61m (£1.38m) made in 14 months since its investment in David Luiz. The fund – whose manager, João Caino, said the investors are a mix of companies and wealthy individuals but do not include football agents – still owns economic rights in 18 Benfica players, ranging from 20% stakes to the 50% bought in the Brazilian striker Alan Kardec for €3m last June.

"Third-party" ownership of any player is prohibited at English clubs, a rule the Premier League introduced after the bitter disputes which followed West Ham signing Carlos Tevez and Javier Mascherano in August 2006, when the Argentina internationals were owned by unnamed investors represented by Kia Joorabchian. The prohibition on third-party ownership now also applies to all Football League clubs.

In Portugal, however, and particularly Brazil, it is still common practice for individual investors to buy stakes in players, speculating that they will cash in for a profit when the players are sold. Benfica, Porto and Sporting Lisbon are floated on Portugal's stock exchange, so they officially announce the sale of players' economic rights, hence the publicly declared 25% stake in Luiz held by the Benfica Stars Fund.

Joorabchian, who sold Tevez to Manchester City in 2009 on behalf of the still-unnamed investors for a fee believed to be £45m, remains Tevez's adviser and has said he is still heavily involved in third-party ownership of players in Europe and South America.

Last June Benfica formally announced they had sold 50% of the Brazil midfielder Ramires's economic rights to a company, Jazzy Limited, for €6m. Then on 18 August Chelsea paid £18m to sign Ramires, who had played one season, 26 games, at Benfica. The deal made a profit for Jazzy Limited of around £4m. There is a Jazzy Limited registered in London, of which Kia Joorabchian is the sole director and shareholder; however, he declined to talk to the Guardian about whether it was his Jazzy Limited which received £9m for Ramires, or about third-party ownership of players generally.

The influential Portuguese agent Jorge Mendes is also involved in part-owning players' economic rights, as well as representing them as his clients in transfer negotiations. His Gestifute agency owned at least 35% of Deco, the Brazilian-born midfielder who played to prominence for Porto. In July 2003 Porto announced they had bought 20% of Deco from Gestifute, in exchange for €2.25m, plus 5% of the economic rights in Ricardo Carvalho and Paulo Ferreira. A week later Gestifute sold another 15% of Deco's economic rights to Porto, this time for 10% of the striker Benni McCarthy, plus €1.25m.

The following summer, after José Mourinho, also a client of Mendes's, moved to Chelsea as the manager, Chelsea signed Carvalho, for €30m, and Ferreira, for €20m. If Gestifute's 5% economic rights were still held in each player – Gestifute declined to confirm that – Mendes's agency would have made €2.5m, on top of the €2.4m in agents' fees which, the Guardian has revealed, Chelsea paid at the time.

Caino, who runs the Benfica Stars Fund on behalf of the bank, told the Guardian the fund aims to be transparent, does not employ any agents, nor does it have agents as investors, because that risked potential conflicts of interest. "The club gains the benefit from the fund of sharing the risk of signing and developing young players," Caino said. "The fund is regulated and all its dealings are transparent."

João Gabriel, a spokesman for Benfica, said the fund did enable the club to receive money up front and share the risk of investing in young players, and also acknowledged that it was a way of trying to manage the club's debts, which stood at €215m in June. Gabriel declined, though, to comment on why the club had sold 50% of the rights in Ramires last summer, so soon before the player was sold outright to Chelsea.