According to People, Sarah Ferguson, who is currently recording a programme for Oprah Winfrey's network, will not be a guest at the event in April.
Ferguson's spokeswoman told the magazine: "She will not be attending. She never expected to be invited."
The representative added: "She has declined all commercial work relating to the wedding."
Princesses Beatrice and Eugenie are expected to attend the wedding with other members of the royal family.