Southampton were expelled from the promotion playoff because a fine would have been insignificant if they had won promotion to the Premier League, said documents from the Independent Disciplinary Commission released on Thursday.
Saints admitted observing a training session held by semifinal opponents Middlesbrough earlier this month, as well as two other similar incidents during the season.
Southampton beat Middlesbrough in their semifinal playoff but were found guilty by English Football League (EFL) of spying on a training session.
Southampton were also docked four points for next season.
The club appealed. But the independent commission, run by Sports Resolution, condemned Southampton's tactics, calling them "a contrived and determined plan from the top down to gain a competitive advantage in competitions of real significance by deliberate attendance at opposition training grounds for the purpose of obtaining tactical and selection information."
The ruling was scathing about what it called "a particularly deplorable approach in its use of junior members of staff to conduct the clandestine observations."
"Junior members of staff were put under pressure to carry out activities that they felt were at the least morally wrong."
Middlesbrough were reinstated and face Hull at Wembley on Saturday for a place in the Premier League.
Southampton appealed to the commission.
"The integrity of the playoff competition was seriously violated," the 12 page document said. It "constituted a deliberate attempt to gain unfair advantage."
COACH'S FUTURE IN DOUBT
The documents said the ruling was unanimous and that the commission believed lesser sanctions would fail to discourage a repeat because promotion to the Premier League is worth an estimated £200 million in extra revenue.
The English Football Association said it was looking at whether it should also bring charges.
An FA spokesperson said on Thursday: "We will now investigate and won't comment further until we have assessed the evidence."
Saints chief executive Phil Parsons meanwhile said the sanctions imposed were "manifestly disproportionate".
Kicking the club out of the playoffs denies them a shot at a Premier League place.
The commission mentioned the involvement of head coach Tonda Eckert, whose future as Southampton boss is in doubt.
Saints, relegated from the Premier League last year, said in a statement that "trust now needs to be rebuilt".
Reports suggest players are considering legal action against the club.
Southampton player of the year Leo Scienza described the punishment as "heartbreaking" and said the club's fans "definitely deserved better".
"We gave everything for this dream," he posted on Instagram. "Day after day, sacrifice after sacrifice, always believing we could bring this club back to where it belongs.
"For me, the dream of playing in the Premier League was something I fought for with everything I had. That's why this pain cuts so deep."
Southampton midfielder Leo Scienza has taken to Instagram to express his feelings on the club being thrown out of the play-offs after the Saints admitted to spying on three clubs during the Championship season. pic.twitter.com/a0qPLvL6sK
— Match of the Day (@BBCMOTD) May 21, 2026
At the 2024 Paris Olympics, Canada's women's team -- the defending champions at the time -- were found guilty of spying on New Zealand, using a drone.
Football's world governing body, FIFA, banned three members of staff, including the head coach Bev Priestman, from football for a year, and docked them six points.
The winners of Saturday's playoff final will join already promoted Coventry and Ipswich in the Premier League next season.