The GAM investor group comprising NewGAMe and Bruellan said it intends to increase its stake in GAM to more than 10%.
It currently controls around 8.4% of GAM's issued share capital.
The group has notified Swiss regulator FINMA of its intention to go above the 10% shareholding threshold, as required by Swiss law.
Investor group challenges Liontrust's valuation of GAM
The move is the latest in the ongoing saga between the GAM shareholders entities involved in the takeover deal, having previously challenged Liontrust's valuation of GAM following the announcement of the acquisition, and criticised the UK asset manager for not providing an alternative cash offer.
At the time, the group said it was considering voting against Liontrust's takeover of GAM.
The shareholders have also taken its concerns to the Swiss Authorities, after raising issues about the exemptions Liontrust had received as part of the deal.
