In an open letter, investors including Aberdeen Standard Investments, M&G Investments and Legal & General Investment Management said that all lobbying by third parties should be consistent with mining companies’ views and producers should exit lobby groups if this isn’t the case.

“Companies should be consistent in their policy engagement with governments and ensure any engagement conducted on their behalf via industry bodies is aligned with the objectives of the Paris Agreement,” the investors said in the letter. “The funding of organizations undertaking lobbying in contradiction with companies’ own stated positions is a real concern which presents material business risks.”

Industry lobby groups have become increasingly controversial, especially in Australia, where the resource sector is highly influential. Investors have pushed mining companies to be more transparent about how their businesses impact climate change, as well as how to guard against future environmental regulation.

Miners such as BHP Group, the world’s biggest, have resisted calls to leave groups, saying they help promote broader benefits to the industry and allow companies to influence positioning on environmental issues. Still, BHP supports the Paris Agreement and has said it will review memberships that have “materially different” positions on climate change.

BHP last year quit the World Coal Association and said in 2017 it would monitor advocacy by other groups, including the Minerals Council of Australia, following a review of its involvement in 21 associations. Rio Tinto Group has said it will walk away from groups that clash with its views on coal mining and climate change.

“Supporting trade associations that are working to undermine or frustrate vital efforts to address climate change presents significant risk to shareholder value,” said Stephanie Pfeifer, head of the Institutional Investors Group on Climate Change, which was involved in drafting the letter. “Contradictory or negative lobbying is simply indefensible.”

Last week, BHP investors failed to force the company to cut ties with lobby groups which are seen hindering efforts to meet global climate-change goals. Just 22% of shareholders supported a resolution at the annual general meeting in London, though Australian shareholders will vote at their AGM next month.