Derby County manager Frank Lampard was unhappy with Leeds United counterpart Marcelo Bielsa's presentation about his unorthodox coaching methods on Wednesday.
Bielsa admitted spies had watched each of their opponents this season, the issue having been raised when a Leeds employee was caught outside Derby's training ground ahead of their clash last Friday.
The Argentinian faced widespread criticism for his actions, including from Lampard, and admitted it was not an isolated incident.
Speaking after his team's FA Cup penalty shoot-out win over Southampton, Lampard was unhappy with the step taken by Bielsa.
"It's certainly a league issue now because it's the league, it's every team, so it's up to them to decide what goes from now," he said.