Former Blackburn manager Sam Allardyce has instructed lawyers to initiate proceedings against his Ewood Park successor Steve Kean, Press Association Sport understands.
The action comes in relation to unguarded comments made by Kean about Allardyce to supporters while secretly being filmed last summer.
The four-minute video, apparently filmed during Rovers' pre-season trip to Hong Kong, was released on the internet overnight.
In the video, Kean makes comments which appear to be critical of Allardyce during his conversation with fans in a bar.
In the footage, in which expletives are used, Kean also appears to predict Rovers will finish in the top half of the Premier League and win the Carling Cup.
Rovers were relegated from the Premier League amid scenes of unrest and protest against Kean and India-based owners Venky's.
Kean has been a hugely unpopular appointment since being promoted from within to replace the sacked Allardyce in December 2010. Despite repeated calls for his removal by fans, Venky's have strongly backed him and are due to meet the Scot for post-season talks in India this week.
The BRFC Action Group, who have claimed responsibility for the footage, have long campaigned against Kean and Venky's.
They appear to have stepped up their activity since demotion to the Championship was confirmed and they have now arranged meetings with Government and the Premier League to air their concerns.
A statement from the group's committee read: "We as a group of supporters, elected by its members, are disgusted that our club has been allowed to be pillaged with very little resistance from the regulatory bodies who should act in the best interest of the sport and supporters."