A petition by Johnny Depp supporters to remove Amber Heard from the Aquaman sequel has gathered more than 1.5 million signatures.

Heard is due to play love interest Mera in the DC superhero film series, but supporters of Johnny Depp have set up an online petition to have her fired from the movie after the actor lost his high-profile libel case against The Sun newspaper.

The petition, which hopes to get a total of three million signatures, was set up by fans who claim Heard "systematically crusaded to ruin Depp in Hollywood" following their divorce in 2017.

Titled "Remove Amber Heard from Aquaman 2" and addressed to the senior vice president of publicity and communications at DC Warner Bros, it has been signed more than 1,547,300 times.

Heard, 34, has repeatedly denied the accusation, telling Entertainment Weekly: "Paid rumours and paid campaigns on social media don't dictate (casting decisions) because they have no basis in reality.

"Only the fans actually made Aquaman and Aquaman 2 happen. I'm excited to get started next year."

The James Wan-directed Aquaman film, starring Jason Momoa, arrived in 2018 and was a box office success, grossing more than 1.1 billion US dollars globally.

Its sequel is scheduled for release in 2022.

Depp, 57, stepped down from the role of dark wizard Gellert Grindelwald in the third Fantastic Beasts film after losing his libel case against The Sun newspaper over an article which labelled him a "wife beater".

He was refused permission to appeal against the judgment last week but has been given until December 7 to apply directly to the Court of Appeal.

Warner Bros Pictures has confirmed that James Bond star Mads Mikkelsen will replace Depp in the role.