Porto have threatened to report Chelsea to both FIFA and UEFA, according to The Sun, with the Portuguese club claiming that Alvaro Pereira was illegally approached over a possible move.
Pereira insisted at the end of the transfer window that a deal for him to leave the club was close to being agreed, but Porto blocked it. The full-back was particularly unhappy about the move falling through.
Chelsea had hoped to gain Pereira’s signature by deadline day, but reports have speculated that Porto wanted revenge over the club that took their manager.
But Porto president Jorge Pinto da Costa told the paper that Chelsea had spoken to Pereira "without Porto's authorisation. They made him an offer."
While Pereira has a £26.5 million release clause in his contract, Chelsea were said to have made two bids for the 25-year-old that were less than that. Porto knocked back both bids, and were reportedly holding out for the Blues to pay the full amount.