Southampton are being severely punished after sending someone to illegally film Middlesbrough's training ahead of the teams' play-off semi-final matches.
An independent disciplinary panel has stripped Southampton of their place in the final. The club will also be stripped of four points in next season's Championship.
A statement from the English Football League (EFL) said Southampton had admitted repeated breaches of the rule prohibiting observation of an opponent's training session within 72 hours of a match. Southampton are also said to have spied before matches against Oxford and Ipswich last season.
The decision means that Middlesbrough, who have been coached by Kim Hellberg since the end of last year, will be allowed to play in the play-off final against Hull at Wembley on Saturday.
Hellberg has repeatedly been strongly critical of such espionage.
"I couldn't believe my ears or my eyes," he said after it was discovered.
Southampton won 2-1 on aggregate in the two-legged tie against Middlesbrough and will appeal the disciplinary panel's decision. The EFL says it is working to be able to hear the appeal as early as Wednesday.
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