Employees of Brighton and Hove Albion Football Club claim they were unfairly dismissed in a “witch-hunt” after team selection was leaked online.
Three members of ground staff were allegedly denied disciplinary hearings or reasons for their sacking on Friday.
The GMB union said the dismissal “stinks” and called for Brighton to reinstate workers.
Brighton, which recently retained Premier League status, said it would not comment on the incident.
The club announced team selections were being leaked from October 2018.
Ex-deputy head groundsman Ashley Smith, 34, said he was taken into “private meetings” and questioned along with his colleagues from April.
The meetings were not recorded and the employees were allegedly told “they were helping with the inquiry”.
“It was a dream job that has been taken off me for no reason,” he said.
“I have a family mortgage and it’s going to have a massive impact on my whole life. I haven’t been sleeping since.”
GMB branch secretary Mark Turner said: “No evidence has been found or presented by the club during this near three-month investigation which links our members to the supposed social media team leaks, yet they dismiss our members without notice.
“This just stinks and considering this club prides itself on its commitment to the standards, values and expectations set by the Premier League, the way they have treated their staff throughout this witch hunt is simply deplorable and unfair.”
The GMB and Mr Smith said the workers had appealed against the decision and union is taking legal advice.