British asset manager Liontrust won the backing of just 33.64% of GAM's shareholders, interim results published on Thursday showed.
A group of investors led by French billionaire Xavier Niel's NewGAMe and asset manager Bruellan have opposed the all-share offer, saying in July that it "grossly undervalues GAM".
"The GAM Board acknowledges that the majority of our shareholders have not found the Liontrust Offer compelling. I am pleased that we have entered constructive and productive discussions with NewGAMe and that these discussions continue at speed," Chairman David Jacob said.
Liontrust had made its offer conditional on winning the backing of two-thirds of GAM's shareholders in a prospectus it published in June.
Liontrust, which has until August 29 to decide whether it will waive the condition and complete the transaction anyway, said it currently expects to declare its offer to takeover GAM unsuccessful on that date.
After a year-long battle against cash outflows, GAM agreed to the takeover in May.
Liontrust offered 107 million Swiss francs ($122 million) in its own shares at the time, a deal now worth considerably less owing to a decline in Liontrust's share price.
The opposing shareholder group, which now controls 9.6% of GAM's shares, wants to keep GAM listed, restructure it and focus more on business with super-rich private clients.
Discussions with the group are now focused on providing a bridge loan, GAM said, adding it expected the group to provide proposals for a board shake-up and an extraordinary general meeting.
($1 = 0.8768 Swiss francs)
(Reporting by Brenna Hughes Neghaiwi and Noele Illien; editing by Friederike Heine and Jason Neely)
