Manchester City allegedly made an illegal payment to Jadon Sancho's agent when they signed the England international from Watford in 2015.
The then 14-year-old moved to the Etihad for £150,000 and went on to spend two years in the club's academy system before moving to Borussia Dortmund in a £7m deal after he wasn't included in Manchester City's squad for a pre-season tour.
In the latest revelation from whistle-blowers Football Leaks, published by Der Spiegel, Manchester City are alleged to have made a banned payment to Sancho's agent when he made the move to the north-west.
Regulations prohibit players under 16 from being represented by agents, but Sancho's representative Emeka Obasi was paid £200,000 by City to scout players in Central and South America.
The Football Leaks revelations, however, cites leaked emails which indicate that Obasi's fee was actually in relation to Sancho's move from Watford to Manchester City.
These latest claims have come after the Citizens breached FIFA and Premier League rules by paying youth player Mathias Bossaerts' family £190,000.
In response to the claims about Sancho's agent fee, Manchester City released a statement claiming that the leaked documents has been taken out of context, adding that it was a 'clear and obvious' attempt to damage the club’s reputation.
Sancho has become one of Europe's brightest players since moving to the Bundesliga in 2017, going on to make 42 appearances across all competitions for Borussia Dortmund where he has scored nine goals and claimed 17 assists.
The 18-year-old has also been pushed into Gareth Southgate's England setup thanks to his form in Germany, with many expecting that he could play a vital role in their upcoming UEFA Nations League matches later this year.