However, it says only European passport holders can apply and "NOT British-European due to new Brexit rules from 1st January 2021".
The film's producer Paul Webster has stepped in to clarify the situation with a statement to Deadline.
British actors have been told not to audition for the role of a young Duke of Cambridge in a forthcoming film about Diana, Princess of Wales, due to new rules faced by the country post-Brexit. "If they happen to have an Irish passport, all well and good. but it's not a hindrance to have a British passport".More news: Hamilton: Salary cap shouldn't hinder young F1 drivers
"Many of our cast will be British".
Diana was previously tackled on the big screen in a 2013 film by director Oliver Hirschbiegel, in which Naomi Watts played the princess and received an array of negative reviews. But this is an official co-production with Europe so we don't anticipate any issue with our British cast working in Germany.
The UK is due to leave the European Union on 31 December 2020. Kirsten Stewart is portraying Princess Diana.
"Once pulled aside, Diana said, "'Camilla, I would just like you to know that I know exactly what's going on.' She said 'I don't know what you're talking about.' I said 'I know what's going on between you and Charles, and I just want you to know that'".More news: Bam signs 5-year, $163M extension with Heat
Although the film is set at Queen Elizabeth's Sandringham estate over three days during Christmas in the early 1990s, when Diana's marriage to Prince Charles was coming to an end, it is to be filmed in Germany with EU-based financiers.
Knight's concept for a non-traditional biopic seems reminiscent of Larraín's earlier movie Jackie, focusing on Jackie Kennedy - as played by an Oscar-nominated Natalie Portman.
Spencer now does not have a confirmed release date.More news: Star India acquires rights to telecast SA vs ENG limited-overs series