Private equity firm Waterton Global Resource Management said on Friday it would call a special meeting of Hudbay Minerals' shareholders after the Canadian miner refused its proposal for changes to its board.
Waterton, which said it owns a 7% stake in Hudbay, had also asked the miner to avoid any near-term acquisition or joint venture in a filing on Wednesday.
Hudbay is in talks to buy Chilean miner Mantos Copper SA, according to media reports.
"Hudbay's recent market performance has been atrocious, as the company currently trades at a material discount to its peer group on multiple key valuation metrics," Waterton said in a statement.
Hudbay, in an emailed response, told Reuters Waterton had been invested in the company only for a short period.
"Hudbay management met with the shareholder for the first and only time on August 31, 2018 and was contacted again by the shareholder on October 3, shortly before it publicly issued a letter and press release," the company said.
Hudbay's shares were down 2.1% at C$5.70 on Friday afternoon.