Ticketus, who are owed £27m by Rangers over the next three years, have pulled out of the Blue Knights consortium bidding to buy the club.
The investment firm had been in talks with Paul Murray, who is spearheading the Blue Knights' bid, over helping to finance a takeover deal.
However, they no longer feel they can justify their involvement to their investors, with this week's Scottish Football Association sanctions adding another obstacle to the process.
In a statement, the London-based firm said: "Following extensive discussions with the Blue Knights, led by Paul Murray, Ticketus today confirms that it has withdrawn from the Blue Knights Consortium after it was unable to finalise satisfactory terms of agreement for its investors with the Blue Knights around restructuring its ticket purchase agreement.
"Consequently Ticketus is no longer able to play a role in the consortium's bid for The Rangers Football Club PLC at this stage."
The confirmation comes amid reports the Blue Knights are close to agreeing a formal partnership with Sale Sharks owner Brian Kennedy, who last week saw an improved verbal bid for the club rejected by administrators Duff and Phelps.
And, despite the Ticketus withdrawal, the Blue Knights are reported to be close to finalising their bid.
Rangers manager Ally McCoist said today: "I spoke to the administrators this morning and they are very close to getting a deal done with a potential purchaser."
Ticketus, who provide football clubs with capital in return for rights to future season ticket income, had been discussing a finance deal that would see them take back £10 million over a longer period, but the firm stressed their foremost duty was to protect their current investment.
The statement read: "Our willingness to work with all interested bidders, and to try and be part of a solution for the club, was undertaken with the objective to agree terms that would satisfy both our investors' needs as well as being in the interests of the club, its fans and its creditors.
"Regrettably over the course of this week it became impossible to reconcile these interests with the proposals put forward by the Blue Knights as the terms of a deal became clearer."
The decision comes in the wake of a £160,000 fine and 12-month transfer embargo imposed by a SFA judicial panel, which the club have appealed against.
More potential sanctions could come on Monday when the Scottish Premier League clubs vote on financial fair play proposals.
Ticketus said: "There have been a number of challenging issues that have emerged over the course of the last month, including delays to the administration process, the SPL's ruling and the recent news from the SFA, all of which have affected the value of the club and added complexity to the bidding process and our discussions with the Blue Knights."
The firm added they were "deeply disappointed" in the breakdown of a deal but stated all parties had acted in good faith and wished the Blue Knights well in their bid to secure the best outcome of the club.
Ticketus will now join the pool of creditors who would have to be satisfied by a Company Voluntary Arrangement, the Knights' preferred exit route from administration.
Murray has previously stated his deal with Ticketus made financial sense as it removed them from the CVA equation.
The Blue Kights' rival, American Bill Miller, has proposed buying the club's assets and transferring to a new company, although his formal offer has yet to materialise as it is dependent on the lack of football sanctions.
Ticketus gave Rangers about £30.5m during Craig Whyte's tenure. Whyte used their initial injection of £24.4m, including VAT, to pay off the club's bank debt and thus complete his takeover in May last year.
The firm are currently the club's main creditor, although Her Majesty's Revenue and Customs could overtake them when the outcome of a tax tribunal is revealed.
Ticketus could pursue Whyte for their shortfall in return given the businessman offered personal guarantees for the investment.
It is understood another option for the firm would be to persuade Whyte to hand his shares to them if they believed that would provide a return for their investors.