The group has offered to buy up to 28 million GAM shares, approximately 17.5% of the issued capital of the firm, at Swiss Franc CHF 0.55 (49p) per share.

The offer represents a 31.9% premium on the closing price of the GAM shares yesterday, and a 29.1% premium on the offer made by Liontrust, it said.

The investor group said the offer would be paid in cash compared to Liontrust's share offer.

Earlier this month Liontrust shareholders voted in favour of the takeover of Swiss rival GAM to form a £53bn AUM fund manager. GAM's board supports the bid.

On Friday Liontrust wrote an open letter to GAM shareholders warning that: “The clock is now at one minute to midnight for the future of GAM. Liontrust’s good and fair offer for GAM is the only one on the table and the only proposal that provides a viable solution for the business leading to a positive outcome for shareholders. There is just over a week left for GAM’s shareholders to tender their shares in support of Liontrust’s proposed acquisition.”

It asked GAM shareholders to back its offer and tender their shares to Liontrust by 25 July.

The partial counter offer may give GAM shareholders pause for thought but may not yet be the last twist in the takeover saga.

NewGAMe is led by Albert Saporta, a hedge fund industry veteran with 40 years’ experience in global financial markets.

Bruellan is an independent provider of global wealth management solutions, headquartered in Geneva, Switzerland.

Albert Saporta, director of NewGAMe, said: "The announced offer gives a partial exit to shareholders who are concerned by the absence of an alternative to Liontrust's inadequate offer.

“As GAM’s second-largest shareholder, we are convinced there is a significant upside associated with the successful restructuring of the company and are confident that GAM shareholders are better off remaining invested in the company."

The offer prospectus will be published on or around 17 August, the group said.

The NewGAMe and Bruellan investor group controls approximately 9.5% of the issued share capital of GAM Holdings and has been pushing for GAM shareholders to reject the offer from Liontrust.

Last week GEM, a New York-based alternatives manager that owns 6.5% of GAM, said it will not be accepting the Liontrust offer.