Rangers director Andrew Ellis has instructed his lawyers to take legal action against Craig Whyte after claiming he is due a quarter of the club's shares.
Ellis claims he was promised a 24.9% stake in the Ibrox club by Whyte when he completed his takeover last May.
He insists the legal move will not impact on a potential sale of the club, with administrators Duff and Phelps set to name a preferred bidder this week.
Ellis told Press Association Sport: "It certainly will not hold up the sale of the club. I'm suing Craig - not the football club.
"I've been trying to sort it out for the last nine or 10 months and I haven't got anywhere so I've handed it over to the legal team."
Ellis is confident he has a strong case, adding: "Without question."
He told the Daily Record: "I am owed 24.9% of the entire club's shares and I will be suing Craig Whyte for it.
"This was part of the initial agreement prior to the takeover and I have correspondence to prove it.
"At the time the solicitors sent all the documents through, Craig accepted the fact that I was getting 24.9% of the club.
"My lawyers wrote to Craig on Thursday about this and we are awaiting his response.
"I do not trust his intentions for the football club and I want to do what I can to make sure the best interests of Rangers are being looked after."
Meanwhile, Singapore-based businessman Bill Ng has spoken of his ambitions for the club if he succeeds with his bid for the stricken Glasgow giants.
Administrators Duff and Phelps are expected to announce this week who has been granted preferred bidder status, with Paul Murray's Blue Knights and American tycoon Bill Miller also in the running.
Ng - apparently a Rangers fan since witnessing their European Cup Winners' Cup success on television in 1972 - was quoted in a number of newspapers saying: "My mission will be accomplished when another young boy watches Rangers lift a European trophy.
"I'm already thinking about the day I can sit down with Ally McCoist and the staff to discuss new signings.
"We want to show that we're not just the type of owners who go in with no understanding and are in it just for the money.
"We will install a board of directors made up of Scottish businessmen who support the club."