Middlesbrough manager Kim Hellberg criticised Southampton for the spying scandal which dominated their Championship playoff semifinal.
A member of Southampton's staff allegedly tried to film Middlesbrough's training last week. Southampton have been charged with a breach of EFL regulations.
But, they beat Middlesbrough 2-1 with an extra-time Shea Charles winner in the second leg on Tuesday to book a place at Wembley Stadium, where they will face Hull City in the playoff final.
An emotional Hellberg said: "I worked 15 years as a coach in terms of trying to get to the Premier League. That's my dream, for 15 years.
"I know there are clubs with bigger resources, there are teams that have more money, there are teams with bigger squads than us.
"What you have as a coach and as a group is the tactical element of the game, where we can beat opponents.
"If we wouldn't have caught that man that they sent up on a five-hour drive, you would sit there and say, 'well done in the tactical aspect of the game' and I would go home and feel like I had failed.
"When someone decides, 'nah, we're not going to watch every game, we send someone instead and film the session', see everything and hope they don't get caught -- I guess that's why he was switching clothes and everything that I have seen on the television -- it breaks my heart in terms of all those things I believe in.
"I think that it's disgraceful. It makes me very sad.
"If we hadn't caught that person, I would be sitting here thinking I should have done better things."
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Southampton boss Tonda Eckert walked out of the post-match news conference on Tuesday, prompted by his press officer, after he was asked by the media: "Are you a cheat?"
The EFL's Independent Disciplinary Commission will deliver a decision into Southampton's conduct.
The rules have changed since Leeds United were punished for a similar spying scandal in 2019. Leeds were punished via the 'good faith' law and were fined, however a new rule has since been introduced which prohibits spying within 72 hours of a game.
PA contributed to this report.
