Singapore businessman Bill Ng has withdrawn his group's offer to buy Rangers.
According to the Straits Times, Ng has released a statement in which he says he has become "increasingly uncomfortable and frustrated with the process of dealing with club administrators" but could relaunch his bid if Duff and Phelps fail to strike another deal.
Ng's decision leaves American Bill Miller as the most likely candidate after Brian Kennedy had a verbal offer rejected and the Blue Knights announced they were stepping back from the process.
The statement read: "Recent developments in the bidding process, with unwarranted and unexplained delays, have prompted our withdrawal from the bidding process.
"After lengthy negotiations with a number of key stakeholders, we have serious concerns over the deliverability of the shares on offer to gain control of the club."
Ng expressed frustration over "ever-increasing uncertainties and complexities in the bidding process".
The chairman of Singapore top-flight club Hougang United had previously expressed frustration with Ticketus, who have a contract to sell £27 million worth of season tickets over the next three years.
Ng has claimed Ticketus increased their demands from £10 million to £17.5 million but he expressed most disappointment with Duff and Phelps, accusing them of "moving the goalposts".
As well as the Ticketus liability, areas of uncertainty around Rangers include the rights of majority shareholder Craig Whyte, an outcome on the tribunal over their potential £75million tax bill and Scottish Premier League proposals on financial fair play, the subject of a meeting on April 30.
Ng said there was "no guarantee" his group would acquire Whyte`s 85% shareholding if they agreed a price.
Despite appearing close to appointing the Blue Knights as preferred bidders a week ago, the process has become increasingly unclear.
The Blue Knights have continued to hold talks over re-igniting their bid and Paul Murray, who is spearheading their campaign, said on Wednesday they arereconsidering their position after initially stepping back on Monday to allow Ng to complete a deal.
Miller is understood to have been considering revealing more of his intentions but no statement has been forthcoming from the businessman, who owns a Tennessee-based towing and vehicle recovery firm.
Duff and Phelps signalled on Thursday night that none of the bids on the table were acceptable in their current form.
Joint administrator David Whitehouse said: "We have had a series of constructive discussions with bidders. We have made it crystal clear to them all that to announce a preferred bidder we need definitive, unconditional bids on the table.
"We understand there are complex issues for bidders to deal with and we do not doubt that all parties want to attain control of the football club. We understand also that those interested in buying the club are working hard to resolve all outstanding issues.
"We are continuing to make representations to all stakeholder groups - including the football authorities - to give clarity on outstanding issues which will help existing bids move to unconditional status."