The English Football League has received a complaint from Middlesbrough over allegations of unauthorised filming by someone connected to Southampton during a training session.
Ahead of the two teams' Championship playoff semifinal first leg on Saturday, the EFL said Thursday it had written to Southampton regarding claims an "individual identified to be associated" with the club had been filming on Boro's private property.
The EFL said the alleged incident was being considered as "potential misconduct" under its regulations.
An EFL spokesperson said: "The EFL has written to Southampton requesting their observations following a complaint from Middlesbrough relating to alleged unauthorised filming ahead of the two clubs meeting in Saturday's Championship playoff semifinal first leg.
"The alleged incident is said to have taken place on Middlesbrough's private property by an individual identified to be associated with Southampton.
"The League is treating this matter as potential misconduct under EFL regulations and will be making no further comment at this time."
The teams will go head to head at the Riverside Stadium on Saturday, with the second leg of their semifinal taking place at St Mary's next Tuesday night.
Southampton reached the playoffs with a fourth-placed finish in the Championship and Boro finished one spot below them on goal difference after both sides secured 80 points.
Middlesbrough declined to comment. Southampton have also been contacted for a response by the Press Association.
The alleged incident is reminiscent of the "spygate" scandal involving Leeds, with then boss Marcelo Bielsa admitting to sending a spy to Derby's training ground before their 2-0 win over the Rams in January 2019.
The Argentinian faced fierce criticism and responded by delivering a lengthy press briefing outlining his coaching methods, but the EFL issued a fine of £200,000 for a breach of its "good faith" regulations, while also announcing a new rule preventing teams from watching each other's training sessions within 72 hours of a match.
Bielsa paid the fine out of his own pocket.
