Swiss specialty chemicals maker Clariant and U.S. group Huntsman abandoned their $20 billion merger deal on Friday, notching a win for activist investors who fought against the deal for months on the grounds it would destroy shareholder value.

White Tale, the investment vehicle of hedge fund manager Keith Meister and New York City-based fund 40 North, had increased its Clariant stake to more than 20 percent, Reuters reported on Thursday ahead of the announcement of the tie-up being dropped.

White Tale's rising stake, coupled with other Clariant shareholders who came out against the deal, left the Swiss company doubtful of mustering the two-thirds support necessary for the merger to go through.

The successful revolt comes amid a wave of investor activism in Switzerland, where Credit Suisse is under attack and Nestle also faces demands for change.

Chief Executive Hariolf Kottmann said Clariant still had options to explore after further talks with White Tale.

"To do a merger of equals ... is one option, to make a large transformational transaction is another option, to continue to stand alone is a third option," Kottmann told reporters on a call where he vowed to remain CEO.

"There are four or five of these options, and they have all pros and cons."