The actress and presenter, who is an acquaintance of Prince Charles’, said her relationship with the royal family meant she was able to sort fact from fiction.
“I know them, so I know it’s all made up and it’s rubbish,” the 75-year-old told Women’s Weekly Australia, reports the Mail Online.
She added: “All the poor actors who are doing their best to copy them, it’s awful. Imagine somebody making up conversations they think you’ve had.”
Lumley claimed she “never” watches the programme and that she didn’t think the royals did either.
Her comments come after the Absolutely Fabulous star branded the show “ghastly” earlier in the year.
She isn’t the only person to raise issue with the historical drama however as Earl Spencer, the brother of the late Princess Diana, said The Crown played “fast and loose with history”.
He called for a disclaimer to be placed at the beginning of each episode explaining not all the scenes were an accurate depiction of the real-life events.
Season four introduced Princess Diana to the programme where she was played by Emma Corrin, who received multiple awards nominations for her portrayal.
In the upcoming fifth series, which will be the penultimate season, Elizabeth Debicki will take over the role from Corrin as the series covers the events of the 1990s.
Imelda Staunton will be playing the Queen, taking over from Olivia Colman, while Jonathan Pryce stars as her husband Prince Philip following Tobias Menzies’ interpretation in series three and four.
Also joining the cast is Lesley Manville as Princess Margaret, Jonny Lee Miller as Prime Minister John Major and Dominic West as Prince Charles.