Influential shareholder advisory firm Glass Lewis has urged investors to support a push from an activist hedge fund that would force Rio Tinto to explore ending its primary London listing.

Glass Lewis, which provides voting advice for major investors, said Rio’s board had not properly engaged with the push for a collapse of its dual-company structure. It has backed the shareholder resolution from Palliser Capital despite accepting warnings from Rio that the unification of its dual-company structure in Australia could cost billions of dollars in taxes.