Uefa and players’ union FIFPro want to strengthen a forthcoming worldwide ban to stop third-party investors from owning player transfer rights, Uefa general secretary Gianni Infantino said yesterday.

Fifa’s phased-in ban on so-called third-party ownership of players, or TPO, comes into force on May 1.

FIFPro and Uefa said they have jointly filed a legal action asking the European Commission to outlaw TPO too.

TPO was banned in Britain at the start of the 2008-9 season when the Premier League discovered that Argentinian players Carlos Tevez and Javier Mascherano were owned by two offshore companies when they signed for West Ham in 2006.

The complaint counters an earlier protest against the Fifa ban filed by the leagues in Spain and Portugal, where TPO is rife.

“Third-party player ownership is a kind of modern slavery, where you see players belonging to investment funds, or other, generally unidentified, corporate entities,” Infantino said.

FIFPro hopes the complaint, if successful, will close loopholes in the Fifa rules.

TPO has been banned in some European countries but is popular with agents and clubs in Latin America, Spain and Portugal. They say it lets clubs sign players who would otherwise be unaffordable.

The leagues’ complaint argues that Fifa’s ban “violates rules protecting competition,” and hurts clubs “with fewer economic resources.”

Critics say TPO encourages players to be transferred for profit-and threatens football’s integrity.

Fifa agreed to ban the practice after a two-year campaign by Uefa, whose president Michel Platini said: “I think we are dealing with a type of slavery that belongs in the past.”