Spencer, who has played matriarch Peggy Woolley (formerly Archer) since 1951, has already shot her final episodes for the beloved drama, which aired July 31, the Telegraph reports.
She told the newspaper that her departure was a long time coming.
“I’ve been trying to retire for at least a year,” she said.
“They didn’t want to lose her character. Every time I tried to quit, they gave me more episodes.”
Peggy was often seen as a traditionalist, a conservative character in the long-running drama that charts the ups and downs of life in the fictional Ambridge.
Among Peggy’s many fans is the Duchess of Cornwall, who last year invited Spencer and her co-stars to Clarence House for a reception to mark the show’s 70th anniversary.
In a statement in The Telegraph, Camilla called Peggy “a veritable national treasure that has been a part of my life, and millions of others, for as long as I can remember”.
While Peggy hasn’t been written off the show yet, Spencer has her own ideas about how best to arrange her character’s exit.
She said: “The simplest thing is if (Peggy) has fallen or something and goes to The Laurels (the fictional nursing home in Ambridge.
“She can languish there for years.”