Revolution Bars Group said the offer had "significant procedural-driven risk".
Revolution Bars Group has said that a bid for the business received from Nightcap is “incapable of being delivered”.
The group, which is behind the Revolución de Cuba and Peach Pubs brands, launched a formal sale process in April alongside a restructuring plan that included raising £12.5m.
In early May Revolution Bars Group said it was in talks with Nightcap over a possible deal, before claiming in was in talks with 32 potential buyers.
In an update the group said it had held an “exploratory meeting with Nightcap plc regarding a range of possible transactions”, followed by a number of follow-up calls, but that “following legal advice, the board has concluded that the Nightcap proposal is incapable of being delivered”.
It added that the Nightcap funding would need two separate equity fundraisings to successfully complete, which would mean funding would not be in place at the time of the planned launch.
Revolution added: “There is significant procedural-driven risk and cost associated with the Nightcap proposal over and above the level of risk that applies to the existing plan.
“This includes the fact that the acquisition by Nightcap of the company would constitute a reverse takeover pursuant to the AIM rules for companies. The implementation of such a transaction would ordinarily require extensive financial and legal due diligence, and the publication of an admission document in respect of the enlarged entity.”