Hudbay said the private equity firm's move was a ploy to stop it from soliciting proxies as a proxy contest between the two parties heats up.

Waterton, Hudbay's second largest shareholder at 12.1%, last year gradually stepped up its dissent, urging the miner to replace its chief executive and nominating its own slate of five directors to the board.

Waterton argued Hudbay's recently filed management information circular related to its annual and special shareholder meeting scheduled for May 7 "contains misrepresentations", Hudbay disclosed.

It said the litigation was "frivolous".

Waterton said in a letter to Hudbay shareholders on Monday that "Hudbay's recent disappointing actions and desperate unprofessional tactics show that adult supervision is urgently needed".

It said the board had ignored a settlement proposal supported by about 35% of shareholders, demonstrating deep entrenchment.

"Hudbay is at a strategic inflection point and desperately requires effective strategic thinking and fresh perspectives on the board to create real value for shareholders."