Everton could be facing a points deduction or a substantial fine over their pursuit of Marco Silva when he was manager of Watford last season.
The long-running dispute between the two clubs escalated on Thursday with reports in The Times that an independent inquiry has been launched into Everton's recruitment of Silva.
The Hornets claimed Everton made an 'illegal' approach for Silva last season and reported Everton to the Premier League.
Any inquiry could require Everton's hierarchy to hand over their phone records and diaries to a QC, who would seek to uncover any contact between the two parties.
The last high-profile 'tapping-up' case saw Chelsea found guilty of approaching Ashley Cole in 2005, breaking Premier League rules in the process.
Chelsea were given a suspended three-point deduction and handed a £300,000 fine.
Cole was also fined £75,000 and then-manager Jose Mourinho had to pay £75,000 for attending a meeting with the defender.
Silva was subsequently sacked last January with Watford citing Everton's approach as a 'catalyst' for his dismissal.
Silva replaced Sam Allardyce as Everton manager at the beginning of June but the saga between the two clubs has rumbled on ever since.
Read more: The Times & The Sunday Times