Joaquin Phoenix reportedly convinced his Hollywood agency to go vegan for its pre-Oscars party

Joaquin also attended the glitzy bash alongside his mother Arlyn Phoenix and fiance Rooney Mara, and the acclaimed actor was seen tucking in to vegan meatballs, according to the New York Post newspaper's Page Six column.

The 'Joker' star is an outspoken advocate for vegan food and he even voiced his support for "plant-based" diets during his speech at the Golden Globes in January.

During his speech at the show, the actor hailed the Hollywood Foreign Press Association for its "very bold move making tonight plant-based".

He added: "It really sends a powerful message."

Meanwhile, Joaquin previously explained that an incident during his childhood convinced him to become vegan.

Asked what prompted him to adopt a plant-based diet, Joaquin shared: "Really it was seeing these fish being killed when I was on a boat as a kid.

"I guess to stun them they were throwing them against the side of the boat. I just had a profound strong reaction. It felt like a real injustice. It wasn't just me, it was my siblings, all of my siblings, except for the youngest, Summer, she wasn't born. My mom was pregnant with her.

"I don't know how to explain it. I think it made me distrustful, and angry, and frightened of humans, humanity. I just thought it was such a gross abuse of power, in a way. I think that during that moment we knew that we were not going to eat meat anymore."