Southampton were charged by the EFL last week after Middlesbrough caught an unauthorised man filming a session at their training ground prior to the play-off semi-final first leg.
Middlesbrough were held to a 0-0 draw at home on Saturday before losing 2-1 after extra-time in the second leg at Southampton on Tuesday.
Southampton are due to play Hull, who beat Millwall in the other semi-final, in the play-off final, with a lucrative place in the Premier League on offer for the winners at Wembley.
Furious Middlesbrough boss Kim Hellberg branded Southampton “cheats” as the spying storm gathered momentum.
Leeds were fined after then manager Marcelo Bielsa admitted a member of his staff spied on a Derby training session in 2019.
But Middlesbrough want a far sterner punishment for Southampton after revealing their request to be part of the independent commission hearing into the alleged spying had been denied.
In response, Middlesbrough on Friday called on the EFL to kick Southampton out in the interests of fairness and to deter clubs from trying anything similar in future.
“The club regrets that outcome, given we are directly affected by the matters under consideration and hold relevant factual evidence as to the events in question and their competitive impact,” a statement said.
“The conduct at issue, namely the observation and recording of our training session ahead of a fixture of such significance, goes to the heart of sporting integrity and fair competition.
“In these circumstances, the only appropriate response is a sporting sanction which would prevent Southampton FC from participating in the EFL Championship play-off final.”
The final is due to be played on May 23, but an EFL hearing may not be heard until Tuesday, placing a question mark over the scheduling.
Given the high stakes involved, an appeal from one or more parties in the case seems almost certain.
However, the EFL said it “continues to plan on the basis that the Championship play-off final will take place as scheduled.”
The league added that it has “a number of contingency plans should they be required.” (AFP)