The actress played the part of Maud, Lady Holland in the revival of the show, which launched last year (10), but she has decided to step down before filming begins on the second season.
A statement from the BBC reads, "It's with much sadness that we say goodbye to her wonderful character, the straight speaking mother-in-law Lady Holland. However, we respect her decision and we will be announcing new star casting soon."
Filming for the second season is due to start in October (11).
Atkins co-created the drama with fellow actress Jean Marsh, who has played housekeeper Rose Buck in both the 1970s series and the revival.