Barcelona are not allowed to sign players from Liverpool for a total of three years due to an agreement made when Philippe Coutinho swapped Anfield for the Camp Nou earlier this year.
Coutinho made the move to Catalonia for £142m, eclipsing the £73m that Barcelona paid to sign Luis Suárez shortly after the 2014 World Cup.
Frustrated that the club's best players were simply being poached by the La Liga giants, radio station Cadena Ser (via AS) claim that Liverpool demanded a clause to be included in Coutinho's move which would prevent their best players from making the same move in the near future.
It's said that Barcelona agreed not to sign players from Anfield for a total of three years, of which two seasons are now left.
Coutinho was signed by Barça as a long-term replacement for their own Brazilian superstar, Neymar. The former Santos forward joined French side Paris Saint-Germain for a world record €222m after his release clause was paid by Les Parisiens.
Along with Coutinho, French winger Ousmane Dembélé was also signed as a way of filling in the gap which had been left by Neymar.
However, the World Cup winner has struggled to adapt to life in Catalonia and is already being linked with moves away from the club, just one year on from his €115m switch from Borussia Dortmund.
Liverpool are understood to be monitoring his future as they look to strengthen their squad, while Arsenal have also been linked with a big money move for the 21-year-old.