Sailingstone Capital Partners, the fifth-biggest investor in Turquoise Hill Resources (TSX: TQR) said on Friday it will vote against Rio Tinto's (NYSE: RIO; LSE: RIO; ASX: RIO) intended US$3.3 billion takeover of the Canadian miner, in a shareholder meeting on Nov. 1.
The activist investor said that Rio's bid not only undervalues the target, but it also intends to take advantage of the "material governance failures" created by independent directors of both mining companies over the last decade.
Sailingstone, a U.S.-based fund manager specializing in resources companies that have a 2.2% stake in Turquoise Hill, had already said it considered the offer too low and "opportunistic."
Rio Tinto announced on Sept. 1 it had reached an agreement after six months of takeover talks to buy the 49% of the Canadian miner it didn't already own for a figure about 20% higher than the original US$2.7 billion bid, which it made in March.
The deal would give the global miner a 66% stake in the giant Oyu Tolgoi mine in Mongolia, one of the world's largest known copper and gold deposits. The remaining 34% is owned by the Mongolian government.
Rio Tinto has had a rocky relationship with the Quebec-based miner, particularly over how to fund Oyu Tolgoi's expansion. Rio has also drawn criticism from some of Turquoise Hill's minority shareholders about the control it exerts over the company.
The global miner, which has mined copper from Oyu Tolgoi's open pit for a decade, and the Mongolian government ended earlier this year a long-running dispute over the $7 billion expansion of the mine.
Rio Tinto chief executive Jakob Stausholm has said the proposed takeover would simplify governance, improve efficiency and create greater certainty of funding for the long-term success of the Oyu Tolgoi project.