A charity focused on rainforest preservation has called on actor and environmental advocate Leonardo DiCaprio to step down from his role as a UN Messenger of Peace for climate change due to his own charity’s reported connection to a $3 billion Malaysian embezzlement scheme.

The Bruno Manser Funds — which in August urged the actor and his Leonardo DiCaprio Foundation to return what it called “stolen money” — repeated its demand at a press conference in London on Friday, according to the Hollywood Reporter.

“If DiCaprio is unwilling to come clean, we ask him to step down as UN Messenger of Peace for climate change, because he simply lacks the credibility for such an important role,” Bruno Manser Funds director Lukas Straumann said, according to THR.

The calls for DiCaprio to resign from his position at the United Nations, which was bestowed upon him in 2014, stem from the actor’s reported connection to several figures embroiled in the world’s largest embezzlement scheme.

According to a Department of Justice complaint, the 2013 film The Wolf of Wall Street — for which DiCaprio won a Golden Globe — was funded with $238 million stolen from 1MDB, a Malaysian sovereign wealth fund holding billions of dollars earmarked for development in the country. Red Granite Pictures, which produced the film, was founded by the stepson of the Malaysian prime minister, Riza Aziz, now a central figure in the investigation into the mismanagement of the 1MDB fund.

The complaint also alleges that DiCaprio’s environmental-focused charity organization received donations or benefitted from auction items purchased with money stolen from the Malaysian fund.

The actor’s charity has faced increasing pressure to return what some have called its “ill-gotten” donations. In an open letter to the charity last month, Malaysian attorney and civil rights advocate Ambiga Sreenevasan expressed “shock” and “embarrassment” to learn that the Leonardo DiCaprio Foundation was, as she put it, “connected with the heist of the decade that has undermined the [Malaysian] people in so many ways.”

Malaysia-based environmental organization Save Rivers has also called on the actor to return questionable donations.

The increased pressure comes as DiCaprio is on a tour of film festivals around the world to unveil his National Geographic climate change documentary Before the Flood. The actor was reportedly in London on Saturday for the film’s premiere at the BFI London Film Festival, and previously premiered the film at the Toronto International Film Festival in September.

Earlier this month, the actor joined President Obama and climate scientist Dr. Katharine Hayhoe for a discussion about climate change at the White House, which was followed by a screening of his film on the White House’s South Lawn.

Follow Daniel Nussbaum on Twitter: @dznussbaum