The Scottish-born actress, formally known as Lady Rix after her husband Brian was made a life peer, died in hospital yesterday.
She appeared in hit shows including Fawlty Towers, Doctor Who and Tenko as well as films including Four Weddings And A Funeral.
The birth of her daughter Shelley, who had Down's Syndrome, in 1951 led the couple into charity work, with Lord Rix becoming chairman of the learning disability charity Mencap.
Its chief executive, Mark Goldring, said: "It is so sad to hear of Lady Rix's death. Lord and Lady Rix made a formidable team in their determination to change the lives of people with learning disabilities. She was, in her own way, just as involved with Mencap and the wider issues of learning disability as Brian and was a powerful advocate and campaigner.
"Elspet made a real difference, in a world where few people really do. We will work hard to ensure that her legacy of campaigning and care will continue.
"Our thoughts go out to Lord Rix and the rest of the family at this very difficult time."
Lady Rix, who grew up in India, is survived by her husband, two sons, a daughter and grandchildren.
Her daughter Shelley died in 2005.