The major sponsor of a Premier League football club is set to be asked to "walk away" from the club over the sacking of three members of its ground staff.
The GMB union is considering legal action against Brighton on behalf of the trio, who maintain they were dismissed without being given a reason.
They were told that the club had lost "trust and confidence" in them.
The union said there was no evidence linking any of the three to claims that team selections were leaked last season, when Brighton narrowly avoided relegation.
GMB general secretary Tim Roache told the union's annual conference, being held in Brighton, that the ground workers had been sacked without being allowed any union representation.
He said: "Sacked by telephone, told only they are not trusted and so will not be part of a reorganisation.
"No investigation, no allegations to answer. That is appalling behaviour by a football club that should aim to have Premier League employment rights to match its Premier League standing."
"The club needs to treat these workers with dignity and respect, otherwise we will be contacting American Express demanding that they walk away from the club."
A club spokesman said: "The club does not comment on matters which it regards as confidential."