A rainforest preservation charity has called upon Leonardo DiCaprio to step down from his role as a UN Messenger of Peace for climate change unless he cuts ties with Red Granite co-founder Riza Aziz and Malaysian financier Jho How, who are linked to an international money laundering scheme.

Speaking at a press conference in London, Lukas Straumann, director of Switzerland-based charity Bruno Manser fund said that DiCaprio had “consistently refused” to explain his ties with “politically exposed persons” linked to the the multi-billion dollar 1MDB Malaysian corruption scandal, which is now being investigated by the US Justice Department.

“If DiCaprio is unwilling to come clean, we ask him to step down as UN Messenger for Peace for climate change, because he simply lacks the credibility for such an important role,” he said.

According to Bruno Manser, DiCaprio’s environmental charity, the Leonardo DiCaprio Foundation, has been the recipient of funds from Aziz and Low. As well as Red Granite co-founder and chairman, Aziz contributed financing to DiCaprio starrer The Wolf of Wall Street. Funds used were allegedly embezzled from Malaysian state fund 1Malaysia Development Bhd, also known as 1MDB. Aziz and Low, the Malaysian businessman who is believed to be at the heart of the operation, both deny any wrongdoing

DiCaprio was named a UN Messenger of Peace in 2014 and UN secretary-general Ban Ki-moon called him a “credible voice in the environmental movement.”

DiCaprio’s climate change documentary Before the Flood, which sees him travel around the world talking to scientists and world leaders about the dramatic changes occurring around the world due to climate change, will have its European premiere at the London Film Festival on Saturday.