The 75-year-old actor has starred alongside Linda Robson and Pauline Quirke as vivacious Essex housewife Dorien Green in the hit sitcom since 1989.
But Joseph told The Mirror at the Hampton Court Palace Garden Festival: "I have lived with her for 32 but she's now rested... rested with her heels.”
She admitted: "I don’t think it’s going to happen again to be absolutely honest. I think after 32 years, I need to do other things. Keeping your weight down to play Dorien is not easy.
"She has to be an absolutely skinny bean and it's not easy to lose the weight, especially when you’ve had Victoria sponge the whole of lockdown.
"As Dorien you could never eat that. But it's coming off now. I’ve just lost 10 pounds.”
The sitcom – about sisters Tracey (Robson) and Sharon (Quirke), who are brought together when their husbands are sent to prison for armed robbery – launched on BBC One in 1989 and ran for 10 years.
Dorien was the sisters' wealthy, snobby next-door neighbour at Tracey's upmarket Essex home and became well-known and loved by viewers for her love of leopard-print and a man-eating antics.
In 2014 it was revived on ITV and ran for three more series and two Christmas specials.
The most recent special in 2020 did not feature Quirke as sister Sharon.
But Joseph dismissed rumours of a feud between Quire and Robson, saying: "I missed Pauline a lot... I love her.”
Quirke, 61, rose to fame for her role in Birds Of A Feather but has gone on to have an acclaimed career as a dramatic actor.
In 2007 she launched the Pauline Quirke Academy for Performing Arts around the UK, and has not acted since 2017.
Robson, 63, now a Loose Women presenter, recently told Good Morning Britain: "I haven't had a falling out with Pauline Quirke.
"She just doesn't want to act any more – we did a Christmas special – Pauline doesn't want to act any more, she wants to concentrate on her academies, that's all.
Watch: Linda Robson denies feuding with Birds Of A Feather star Pauline Quirke