Earl Spencer spoke out about the series for the first time since it debuted his sister as a character.
The fourth season of Peter Morgan's drama is currently charting the royal family's lives from 1977 to 1990, including the marriage of Prince Charles (Josh O'Connor) and Diana (Emma Corrin).
Episodes featuring Diana have spent time showing her bulimia, struggles with Charles and the pair's extra-marital affairs.
But, Morgan as admitted to taking artistic licence with several plot points, which concerns Spencer.
He said he believes that some people believe everything they see in the show.
Speaking to Alan Titchmarsh on Love Your Weekend, he said: "The worry for me is that people see a programme like that and they forget that it is fiction."
"They assume," he continued. "Especially foreigners – I find Americans tell me they watch The Crown as if they've taken a history lesson. Well, they haven't."
Spencer added: "It is very hard. There is a lot of conjecture and a lot of invention, isn't there? You can hang it on fact but the bits in between are not fact."
He also revealed he turned down producers' request to film at the Spencer family home.
Find out just how accurate The Crown’s latest season is hereyyyy.
