Leeds United have been fined £200,000 (€228,000) and given a severe reprimand by the EFL after an investigation into spying.
The Championship promotion chasers had been under investigation after boss Marcelo Bielsa admitting to sending someone to spy on Derby at their training ground ahead of their match against Leeds last month.
The club formally admitted a breach of Regulation 3.4 which states: "In all matters and transactions relating to the League, each Club shall behave towards each other Club and The League with the utmost good faith."
Leeds say that they have agreed to support new EFL regulations that will make it clear that clubs are expressly prohibited from viewing opposition training 72 hours prior to a fixture unless invited to do so.
In a joint statement with the EFL, Leeds said: "We accept that whilst we have not broken any specific rule, we have fallen short of the standard expected by the EFL with regards to regulation 3.4.
"We apologise for acting in a way that has been judged culturally unacceptable in the English game."
In an extraordinary media conference after his spy was caught, Bielsa revealed that he routinely scouted opposition training sessions.
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EFL chief executive Shaun Harvey said: "The sanctions imposed highlight how actions such as this cannot be condoned and act as a clear deterrent should any club seek to undertake poor conduct in the future.
"I would like to thank Leeds United for their assistance in helping to bring this matter to a conclusion as quickly as was practically possible.
"We will now look to move on from this incident and commence the discussions about introducing a specific regulation at a meeting with all clubs later this month."